THE AUTOBAHN
GERMANY‘S EXPRESS HIGHWAY SYSTEM

Thai: for the Doom of B. S.
MICHIGAN STATE COLLEGE

Gerald E. Herr
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THE AUTOBAHN
GERMANY'S EXPRESS HIGHWAY SYSTEM

A Thesis Submitted to

The Faculty of
MICHIGAN STATE COLLEGE
of
AGRICULTURE AND APPLIED SCIENCE

by

GERALD E. HERB
Candidate for the Degree of

Bachelor of Science

March 1949

TH Esrs

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. Along the German Autobahn

ACKNOWLEDGMENT

The author wishes to express his grateful
appreciation to his wife, Marie, whose willing and untiring
help and consideration have made the completion of this
thesis possible sooner and with less effort on the author's

part.

Acknowledgment is also given to Mr. Gail Blomquist
whose help and suggestions lead to the reception of much of

the material used herein.

The pictures used are by courtesy of "The Canadian
Engineer," "The Engineer," and the United States Public Roads

Administration.

CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . . . 1
Chapter I - The Autobahn Is Conceived . . . . . . . . . . 5
Chapter II - Reasons for Building the Autobahn . . . . . . .8
Chapter III - Organizing and Financing the Autobahn . . . . 15
Chapter IV - Scope and Descriptions of the Autobahn . . . 22
Chapter V - Construction Progress Made and Materials Used.51
Chapter VI - Specifications and Construction Methods . . . 62
Chapter VII - Condition of the Autobahn Today 9 . . . . . . 96

Chapter VIII - Conclusions and Recommendations . . . . . . .113

Bibliography . . . . . . . . . . . . . . . . . . . . . . . .117

INTRODUCTICN

This is the story of a great system of highways, their
conception, financing, construction, use and present condi-

tion. This system of highways is known as the "German

Autobahn."

Since soon after the development of the automobile and
its more prevalent use by the common people, the German
government had realized the need for a more adequate system
of roads. No one in the government had any definite plans,
however. Certainly no one even imagined the need for a vast
system of eXpressways -- until Hitler came to power. His

plans for Germany changed many plans and ideas in other

minds.

Perhaps a brief description here of the type of road
the Germans built will aid the reader in understanding the
scope of the project and the care with which such a project
was necessarily undertaken. The German Autobahn was fashioned
somewhat after the Italian Autostrada. These two highways
are very similar, but different from our common highways.
Thesecnuntries had different ideas than we have as to what
is meant by an expressway. We understand that an eXpressway
is a wider, straighter road on which we can travel faster and
save time, but they went further. The only road we have which
can compare to the Autobahn is the Pennsylvania Turnpike. The
German expressways are highways that are especially designed

to avoid passing through centers of dense population, to be

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absolutely free from grade crossings, to follow a straight
line as nearly as possible and to exclude all unauthorized
persons and vehicles. The term expressway presupposes an
ideal paving surface, a well-designed location and all
technical equipments for the needs of express motor traffic.
To this end the designers used every bit of knowledge avail-
able and considerable imagination,together with high speci-
fications and good materials to produce what is considered

one of the greatest roads in the world.

CHAPTER I

THE AUTOBAHN IS CCNCEIVED

The people of the world as a whole know very little
about the plans Hitler had in his mind when he became
Chancellor of Germany. One thing is certain; he did have very
definite plans, and he wasted no time in putting them into-
action., It is believed that the time Hitler spent in prison
provided him with plentiful opportunity to think of and
develop his plans. /Cne great part of these plans was the con-
struction of a super-highway system that would link all
sections of Germany.y Whether or not his big plan then was to

conquer the world is unknown.

Soon after Hitler was released from prison, he
began campaigning for the office of Chancellor. He made many
promises which attracted the attention and votes of the common
people. Apparently they were not accustomed to politicians
and their campaign speeches. They put him in office and
anxiously awaited the fulfillment of his promises. Hitler's
International Labor Day speech on May 1, 1955, hinted of a
vast public works program and a plan to induct all German
boys into manual labor. Highways especially would be developed,
he said.//At that timein Germany unemployed persons could be
utilized for road work as "compulsory workers," as "emergency
workers," or as "voluntary workers." The law stated they

r

must (if provided with) work for their compensation They

did not work a 48 hour week, but only 2 1/2 to 5 days. The

-5-

work that they did was work that would not ordinarily be
done, it had to be productive in nature, temporary, and of
public value. Hitler wanted to make use of this law and

out all the unemployed to work on the new roads.

The unemployment situation was Germany's biggest
problem, one-third of her capable workers being on the
unemployed register. This was the ideal time for Hitler to
introduce and promote his plan. He had two good points to
argue: the project could serve the double purpose of

-‘

relieving unemployment and of developing automobile traffic.

Previous to 1955, the highways in Germany were of
such a nature as to not encourage the use of motor traffic
to any great extent, being largely narrow allowances with
paved or macadam surfaces, and not kept in too good a state
of repair. Naturally, the design of any new system of roads
had to take into consideration the c nditions that then
existed in Germany and still do exist in most European
countries. These conditions were employed in the German
conception of an express-way systent In Germany not only
are roads narrow and crooked, but the custom of driving herds
of livestock over the highways is a common one; there is a
large amount of horse-drawn traffic; there are sections
where the ox cart is in general use, and with the improvement
of surfacing since 1950 came a great upturn in the use of
bicycles. Operation of passenger automobiles on such roads

obviously was highly unsatisfactory. Most towns even had

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‘7 i I |.' I'.‘ ‘III I l l ‘ Ill"

 

ordinances giving the bicycle the ri ht-of—way over the
automobile. A tourist traveling through a town on the main
road was not even allowed to blow his horn at a bicyclist,
no matter what the bicyclist did. A motorist who struck a
pedestrian or a bicyclist was always at fault. A horn on
an American automobile was a source of curiosity to the
children and even some adults, for it seemed louder to them

than the largest truck air horn would seem to us.

Even when new roads were built to by-pass the
abrupt turns and the congestion of villages and towns,
immediately the new road became a preferred site for industrial
plants and residences, and in a short time it was almost as

congested as the route through the heart of town.

What is now Germany formerly was a group of inde-
pendent states that had no connecting system of roads.
Establishment of the empire in 1871 did not change the
situation greatly. Roadbuilding was left almost entirely
to local authorities. They ccncentrated their efforts upon
maintaining existing roads which for the most part followed
the haphazard courses dictated by the needs ofcmher centuries.
Thus, prior to World War I little had been done in the 18
German states to fashion roads for automobile use. After
the war rather extensive highway improvements were undertaken
in the areas immediately tributary to cities. But this was

neither sufficient nor efficient.

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yEitler got to work immediately after making his
Labor Day speech. He convinced the cabinet that an express
system of highways was needed, and on June 25, 1955, the
cabinet passed a law for the construction of a network of
highways to cover all of Germany? Plans were drawn up for
the new system w ich was to be built gradual y to supplement
the present highways by a system of main thorough-fares
which would carry auto traffic over long distances, the old
roads serving as tributaries. The general management of the
construction was appointed to the Reich railroad system, and
work was to be started immediately. However, it was
“(September 25, 1955 when Hitler turned the first spadeful of
dirt to get the project underway. At first the work was
very slow; there was no coordination between the highway
departments. Also, the idea of the railroad doing the work
without supervision and inspection by highway and government
officials did not satisfy Hitler nor his cabinet. They
decided to fill two needs at once -- that of control of the
expressways and centralization of all highway departments.
On March 26, 1954, German highway administration, formerly
divided between 26 state and county and 500 independent
township highway departments, was centralized by enactment
of'law. Failure largely of these decentralized authorities
“to cooperate had prevented any real system capable of
Ineesting modern traffic needs. The law provided a chief
ernzineer for all German roads to whom the state and county

hdjzhway departments were subordinated. The new law divided

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all roads into four classes: (1) expressways, (2) federal

highways, (5) state highways, and (4) secondary roads.

The construction and maintenance of the express-
highways was delegated to a special company, called
"Reichsautobahnen," which was legislated by its own law and
financed by qovernmentbonds. These bonds were to be amortized
by a toll paid for the privilege of using the hiqhways, and
justified by the savings to the motorist in oil, gasoline,
tires and repairs. However, after some of the roads were
opened, the idea of the toll was decided against and the road
was free. The cost of the federal highways was financed by

the Reich, and those of the secondary roads by the counties.

The administrative office, which paid for the roads,
also owned them, which was not the case before the new law.
For the through ways in cities and municipalities occasionally
the federal, state or county government paid for as much as
18 feet of width of the street if the community had no great

economic advantage from the thoroughfare.

 

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CHAPTER II

REASONS FOR BUILDING THE AUTOBAHN

Before going any further into the financing and
organization of the system, let us examine the reasons
that were given for Germany's embarkment on such a large
program. To be sure, a highway system was needed, but what
of the Autobahn? Was a highway of that proportion justifiable?
History bears out how justifiable it proved to be, but at the
time of its conception Germany was weak and small, and no one
thought her foolish enough to embark on a "conquer the world"
campaign. 80 excuses and reasons had to be provided for a
curious world. Facts and figures that could not be disputed

were necessary.

The British were among the first to question the
plan, in view of the fact that Germany's roads were much
less extensively used than those in Britain or France. The
German engineers were quick to reply that they were building
for the future. They realized that the present traffic did
not warrant the program, but they were certain the future
traffic would require a perfected road system. They explained
that the plan was instigated at that time in order to alleviate
the unemployment, that like President Roosevelt, Chancellor
Hitler was determined to lose no time in getting axbublic
works program under way. To be sure, the employment situation
was serious here too. Reemploymen , to both leaders, was a

problem of first importance. More than 5 million Germans

-8-

were out of work in 1955. An estimate of unemployment in
the United States (with twice the population) at the same
Itime exceeded 14 millions. It was expected that 500,000 to
600,000 people would be engaged directly and indirectly in
the construction of the highways, and in the production and
transportation of materials, doing away with much of

Germany's unemployment problem.

While Germany was prompted to undertake this
program largely as a means of providing employment, that was
not the only reason actuating the policy. Roads suited for
automobile use were recognized as essential to theystimulation
of the automobile industry. It was found that that industry
would produce more value per persen than any other large
industry, and what is more, it provided customers for another
great domestic industry -- that of making motor fuel from coal.
All this meant that the express roads made possible much

indirect employment.

In 1957, with one third of the system in use, it
was fcund that the results had exceeded expectations: The
output of the automobile industry had drubled in less than
two years and motor car registrations had increased from
661,900 in 1954 to 945,000 in 1955. In July, 1955, there
were 497,000 private cars, 152,000 lorries and 519,000 motor
bicycles. In July, 1957, there were 1,125,000 private cars,

522,000 lorries and 1,527,000 motor bicycles.

But the world's curiousity was still not appeased.
Traffic was increasing rapidly, but outside of a very few
big cities, which were crowded only at holiday times, ;n the
opinion of the British especially, nothing like congestion was
experienced. They felt that the old main roads, with a total
length of 220,000 km., could meet any likely traffic require-
ments quite easily with only slight improvements. They argued
that even the cheapest car was far out of the reach of the

bulk of wage earners.

Therefore these reasnns were soon found publisned in
British and American magazines: (1) thickly settled communities
are close tOgether in Germany; (2) the streets of the old cities
are narrow; (5) gasoline prices were high: and (4) the former

subvention of the German railroad by the Reich.

1. The most important of these is that Germany is
much more thickly settled than the United States, and the
construction of bypasses, which would be the natural
resort to accommodate express traffic, would create
travel distances at least two or three times greater
than the straight line between two points. Also, where
the settlements are so close together as in Germany,
the highway would consist almost entirely of a large
number of bypasses. Traveling on such lines is naturally
very costly and slow and destroys the general advantage
of using highways.

2. On account of the age of German cities the

streets are mostly very narrow: and since most of the
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buildings (that are left now) are of great historical
value, the streets could not be widened. I think now
however, that a areat many streets have been.widened
and the buildings moved or removed by bombs and shells,
not of course at the consent of the German people.
Perhaps another system of highways planned now would
not have so much difficulty. But at the time the Auto-
bahn was planned, the traffic had a very low Speed
limit; yet, in Spite of the low speed, there was a
relatively high number of accidents, which was another
argument for large highways.

3. Gasoline was three or four times as expensive
in Germany as in the United States, and so from the
standpoint of economical operation there was a further
need for highways on which one could maintain a steady
and reasrnable speed. The slow-downs and stops in the
numerous congested cities made long travel by car very
expensive. Experiments show that traveling on an express-
way saves 20 to 55 per cent of the costs of operations.

4. The German railroad, which was indirectly
Operated by the Reich had always had the advantage in
competition with automobile traffic because of an already
existing and highly developed track system anh because
of the benefits arising from general subvention by the
government. This subvention had its chief origin in the
fact that the German railroad had to pay a larqe part of

the war (World War I) debts. The success of this traffic

-11-

policy of the Reich was another cause for the stafination

of automobile traffic.

The government hOped to stimulate the public to an
increased use of motor traffic by ofnstructing this system
of ideal highways,and to further help this cause the yovern-
ment ordered the abolition of all fees and other charges in
connection with the purchase of new automobiles. (Such a
law as that would indeed be welcomed in this country now, too.)
The German government felt that by providing these roads and
removing taxes from motor vehicles the number of motor users
would be yreatly increased: the Reichsbahn would be relieved
of much unremunerative short-distance traffic and mrny non-
paying lines could be closed. Germany was building roads
25 years in advance of traffic requirements. At the same time
England was 25 years behind -- building the Silvertown Way
25 years after the need arose. It looks as though the British
were jealous and trying to rationalize their landing by
questioning Germany's reasons. We, here in America, will also

do well to take a lesson in pl nning for the future.

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CHAPTER III

ORGANIZING AND FINANCING THE AUTOBAHN

The British, Canadians and Americans were not
the only people who had their doubts about the new road
system. Even some Germans, who did not view the new scheme
through spectacles of party enthusiasm had a few doubts
about the project. Germany already possessed the best roads
in Europe (with the possible exception of Italy). Compared
with American or even French or British standards of road
traffic, they looked deserted. It seemed possible that the
present system of roads could carry 10 times the existing
traffic. Only when the future was viewed optimistically did
it seem possible that sufficient traffic would develop to
liquidate the cost of the scheme. Therefore this chapter is
devoted to the different met ods that were u;ed to finance

the Autobahn.

The "Autobahn" law created a new company for the
construction and maintenance of the express highways; the
German Federal Railroad Corporation, which was uovernment
controlled, was authorized to oraanize a subsidiary known
as "Reichsautohahnen Gesellschaft" (Government Auto-Ways

Company).

The railroad was chosen to supervise the construction
because they already had a highly trained and eijcient staff
of specialists for railroad earthworks, bridTes, approaches,

etc. The experience of these men was used for the construction

-13..

of the subqrade. Noreover, the close union between the rail-
road and the highway was supposed to abolish the old destructive

competition of railroad and motor vehicles which was paid for

by the public.

The head of the new

of the

concerning the location of the hithways and

Hitler appointed Dr. Todt to this position.

company was

the chief enoineer

German adninistration, who made the final decisions

their desizn.

Todt worked with

the German railroad, which also had charfe of the counties,

townships and municipalities.

expressways and the other highway

Thus a link between the

system was guaranteed, and

the new ordanization had only to supervise the technical

execution of the cooperative work

departments.

The new company divided
distr cts,
to adiust the construction of all
at the

a central bureau capital.

were not made on the basis of the

but purely onthe basis of unified

on the ground that eaC‘

of railroad and highway

the Reich into eleven

district was better able
local conditions than was
These elever districts
old political divisions,

traffic regions. These

districts contained fifteen main construction offices and

eighty regional district offices.

The actual design and

execution, subject to standard requirements, proceeded from

the fifteen provincial offices with considerable direct

discretion on details and design of bridges and other works

to meet local conditions and need

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Before the exact plans for the Autobahn were drawn
up many studies were made. Dr. Todt had been chosen as
general inspector of German roads with authority, to prepare
and complete a national road scheme. To this end the road
systems of other countries and the methods of adaptation to
motor transport, which they had evolved were reviewed, and
this included, among others, such special subjects as the
Autostrada toll motor roads in Italy, rapid concrete road

construction and expressways in the United States, and method

of surface construction and road widening in Great Britain.

With reference to the first of these, Mussolini
was Hitler's model in this as in many other projects. One
of the first and most efficient of ihe great automobile super
hishways in the world (The Autostrada) was built in Italy
soon after Mussolini came into power. The truck highway
between Milan and Genoa had just been completed in ;952, so
Hitler sent hishinister of Labor to Italy to study the Italian

automobile road system.

The result of these studies was a motorway which
combined and embodied innumerable features in design and
construction rever afipmpted in Canada or the United States.
The foremost and most lastinq impression created by ~
inspection is the complete sense of safety and security and
the total absence of monotony. Naximum safety of movement,

maximum traffic flow and low cost of operation, highest

attainable standards of visibility, and the straightest

-15..

alignment possible are adcitional features attained.

Although the design of the roads was the most
modern that could be conceived, it must be remembered that
the program was instigated primarily to relieve unemployment.
this aim greatly affected the technical methods employed in
the construction of the roads. The use of machinery was
discouraged; local stone, which meant local labor, was used,
and much avoidable expense was incurred. The whole construction
program was carried on with dom stic materials. This meant
that no precious foreign exchange was employed. The Whole
operation was carried on with marks. With a managed currency
there was plenty of domestic money. There was no need for
dollars, francs or pounds. No foreign loans were floated.
The money was supplied by domestic borrowing. The German
peOple readily bought the bonds of their government. Even if
the cost rose as high as 2 million marks per kilometer
($800,000 per mile) as some prophesied, Germany felt she could
justify the project for the reasons given in Chapter II.

~¥

But the people did not supply all of the money
with bonds. The State Railways, which was in control of the
new company3¥put up the first 50 million marks ($20,000,000)
for initial construction. Subsequently the bulk of the
finance was provided from "he newly established on billion
mark fund provided to carry out the "Hitler Employment Plan."
Ultimately, the government controlled a German State Traffic

Company, which included all rail and motor traffic. This was

-15..

characteristic of the dictatorial policies which German govern-
ments had pursued for the past decade in working out the diffi-

culties between rail and motor transport.

It was planned that not only would the railroads
benefit from use of the roads, but many of its staff would
become permanent members of the new system. 0f the new
company's permanent supervisory staff of nearly 5,000 men,
one-fifth were railway officials furloughed to the Auto-Ways
for the construction period. Some of those men would not

return to the railroad.

Hitler's recovery program got underway; in June
of 1955 more than 200,0C0 men had remained employment; the
first contract was let on the first 5,0(0 mile unit of the
road system, and industry and the retail trade was freed of
their fear of country collapse through continued depression.
By the middle of August of 195; two million were back to work,
most of them being employed in jobs created by the road
construction program. Also in August, 1935, the State Rail-
ways announced that they were going to enter the motor truck
transportation field with an initial purchase of 2,000 motor
trucks. The railways allotted a minimum of 10 million marks
for the purchase of truck equipment and establishment of
trucking service, including motor parks, terminals and other
facilities. This was a service long needed in Germany. Since
the railroad had always had a monopoly on the transportation

and freight business, there was no competition to create a

-17-

fast delivery service. Not that a railway owned trucking
business would provide competition, but it did show that the

need was realized, and that an attempt to correct it was made.

The character and scale of the methods of construc-
tion attracted a good deal of attention in other countries
where traffic problems were more acute than in Germany. A
party of experts, politicians and interested persons, visited
the Reich to inspect the roads 3 d their construction in
1937. The most important Question which they raised was the
cost of the operations. fihat the c_mplete scheme would cost
was not stated, but the outlay to date was known. Up to 1957
the sum paid out on capital account was Rm. 1,759 millions.

Of this amount Rm. 1,407 millions had been paid to the private
contractors who had actually built the roads, divided thusly:
some Rm. 590 millions were spent on earth and rock works;

just over Rm. 400millions on the road bed, bridges and culverts;
about Rm. 307millions on surface wort; and Rm. 115 millions

on the provisions of workers' camps, other so ial amenities

and miscellaneous works. The balance of some Rm. 532 millions
of Reich expenditure was used to pay for the carriage of
materials to compensate land owners, and to meet interest and

amorti7ation charses.

Notice that compensation to land owners is mentioned
as a minor item. It is interestinw to compare the difference
in cost of that operation there as compared to this country.

It is true that the Autobahn was designed to miss all cities

and therefore much expense was avoided, but still the expense
was tremendously low. An expressway built here usually begins
or terminates in the heart of a larqe city, or crosses the
whole city. Such a hifihway is the John Tedqe Exnressway in
Detroit. Land owners there hold out for the highest possible
dollar and often get much more for their property than it is
worth. Despite Germany's international importance industrially,
she still remained predominantly an agricultural country.

Thus not only were land wflues low, but also the population

was more sparsely scattered than, say Great Britain. Two

great difficulties which would have to be faced were new

m

rterial roads to be constructed there were of small importance
in Germany. Routes to be followed by the roads were chosen
with a freedom impossible in a country where the land is

much built up and Wh re villages and towns are closely Spaced,
and the ground required was usually obtained at a cheap rate
by normal purchase. then proprietors refused to sell, the
land was oxpropriated. Up to the end of July 1956, out of a
total of lOéO million marks spent on the Autobahn, only

58 million marks went to the purchase of land or rieht of
way. This figure represents a much larger percentage than

it is however, for by the middle of 1956 about 4,000 miles of
route had been purchased and surveyed whereas only about

1,000 miles of road was completed and open to traffic.

The money was raised in various ways. Capital

eXpenditure was, in general, provided by short-term operations;

-19..

with the help of a Reichsbank rediscount credit in 1964 and
1965; and by loans from other sources, including the Reich
Unemployment Board. Railway Corporation cred ts vere raised
for motor-road construction, and were 1 ter funded. On
November 11, 1966, the import and excise duties on gasoline
and benzol were increased, and the price of motor fuel was
raised accordinely. Further, the traffic tax was extended
to include motor passencer and moods services conducted for
gain. There-was a small operating revenue, derived mainly
from gasoline stations. No tolls were collected for the use
of the roads; and it was believed that the higher gasoline
prices were counterbalanced for the motorist by the saving

of time,fue1, and wear and tear, which the new road afforded.

The very success of the scheme aided in the pro-
duction of the necessary funds. As much as 65 per cent of
the funds expended, it was estimated, would otherwise have
been necessary for unemployment relief, while the general
increase of prosperity provided, in the form of increased
returns from taxes, 25 to 60 per cent more toward the cost.

.The rest of the cost was financed by loans as already stated.

In the construction of the roads, the relations
between motor traffic and older forms had to be taken into
account. In 1966 it was estimated that the railways were
losing some Rm. 600 millions of traffic annually to the
roads, but that to counterbalance this in part the motor

:fndustry was bringing new traffic to the railways to an

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annual value of some Rm. 150 millions. The gross revenue of
the railways in 1956 was Rm. 5,985 millions, and the net loss
was thus considerable; and in 1955, the Nazi Government,
intent on the development of the motor industry, had refused
to qive a monopoly of commercial motor transport to the Reich
Railway Corporation. In 1957, local road transport for gain,
if conducted entirely within a radius of 50 miles, was un-
restricted; but outside that radius all long distance carriers
were compulsorily amalqamated in a Reichskraftwaaen-Vertriebs-

verband.

Such in outline is the purpose, character and
economics of these roads. They provided work for the unemployed,
and cost over a million marks per kilometer to construct.
While they were not needed for German traffic and may, in some
cases, have diverted the use of good apricultural land, they
are a source of pride to the German people. And they are a

pattern and example for road engineers in other countries.

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CHAPTER IV

SCOPE AND DESCRIPTION OF THE EUTORAHN

The Autobahn was designed to be the best in the
world and was built to form a net of arterial roads which
covered all of Germany. This chapter is dedicated to the
examination of that design, and the area and cities which

the roads enveloped.

The roads were designed with eight specific
requirements in mind: 1. Total exclusion of pedestrian,
cycle and animal traffic; 2. Complete separation of
opposing traffic streams; 5. The elimination of the
"collision points" arising from one traffic stream crossing
another; 4. The use of over or under bridges to secure
such separation; 5. The control of traffic at road
junctions by clear and systematic layout for each class of
intersection; 6. Provision of a clear and simple system
of road signals; 7. No right of access from adjoining
frontage lands; 8. All advertisements, poles and disturbing
factors on or near the road suppressed. These shall all be

enlarged upon later in the chapter.

First, let us examine the scope of the system. The
program involved the construction of six principal highways,
two of which crossed the country from north to south, three
from east to west and one in the northwest and southeast

directions.

-22-

The German motor-road system, as originally planned,
apparently contemplated the construction of approximately
5,000 miles of four-lane divided highway connecting all of th
larger cities of the Reich. Of this total, only about 2,500
miles were completed due to interruption by the war. An
examination of the map included herein will show many gaps

in the system.

Broadly Speaking, the scheme comprises a circular
road around Berlin, from.which the main Autobahn radiates.
The radiating roads extend to East Prussia, to Gleiwitz
through Rreslau, to Nunich and the Austrian frontier, to
Yarlsruhe throuch Frankfort, to Aix-la-Chapelle through
Hanover, Essen and Cologne, and to the Danish frontier through
Hamburg. These main radiating roads are linked up by a

number of crossroads.

The location of the highways follows a somewhat
tortuous course across the country, especially where the
topography is at all rolling, This is due to their desire
not to interfere, any more than necessary, with the natural

features of the country.

A picture of the area served by the German express
road progranay be had by comparison with a similar area in
the United States. A system of through highways serving the
American cities would cover a territory of somewhat similar

extent: Detroit, Toledo, Cincinnati, Richmond, Va., Washington,

-23-

    
 

- APPROXIMATE SCALE - was
6 if 765 3

) Projected Autobahn

 
   
 
   

 

9

  

 

 

.I’
Uncueui

A mm

,--—W --—.--—.‘~.w -~ ,‘ r‘. ,4 v—

Figuro 1
The German Autobahn System

-24-

Baltimore, Philadelphia, New York, Boston, Buffalo, and
Pittsburg. In Germany the key points are Hamburg, Bremen,
Hanover, Essen, Cologne, Frankfort, Karlsruhe, Stuttgart,
hunich, Nuremburg, Dresden, Breslau, Beuthen, Berlin,
Stettin and Koenigsberg. Population in the German area is

nearly double that of the American area delineated above.

The plans first made called for the system to be
built in three units. The first was to be about 5,000 miles
of road and would require the transportation of 260,000,000
cu. yd. of earth, 54,000,000 bags of portland cement and

550,000 tons of steel for bridges, approaches, etc.

The Autobahn network was intended solely for the
use of motor traffic; horse-drawn vehicles, cyclists and
pedestrians were not permitted to use it. This restriction
of the roads to the requirements of one class of vehicle
considerably simplified the design as compared to arterial

highways in this country.

The Autobahn was built to three different standards
which may be roughly defined as suitable for flat or nearly
flat lowlands without any considerable obstacles, for hilly
regions, and for mountainous districts where the higher
standard maintained elsewhere could not be justified on

economic grounds.

-25-

The constants of design based on those three types of

country are as follows:

TYPE OF LAND LCW LANDS HILLY MOUNTAINOUS
SPEED FACTOR: 110 MPH 95 MPH 80 MPH
MAXIMUM GRADIENT: 4 per cent 6 per cent 8 per cent

RADIUS HORIZONTAL
CURVES: 6000-6500 ft. 2600-5500 ft. 2000 ft.

MININUR RADIUS
VERTICAL CURVES,
SUNEIT :55,000 ft. 50,000 ft. 16,000 ft.
DEPRESSION :16,500 ft. 10,000 ft. 10,000 ft.

Obviously the specifications for low lands could not
be held in mountainous country for economic reasons. However,
it was specified that the transition from a higher to a lower
standard should be gradual, and that the change ought to be
revealed to a driver by alteration of the character of the
landscape. This condition by itself set a lower limit to the
length of any section maintained at onestandard, but the
Inspector-General reserved the right to impose different
lengths if he deemed it necessary. The standards were based
principally upon theoretical considerations of the require-
ments of a vehicle moving at high speed, modified to some
extent by practical knowledge. With foresiaht for the future,

rather remarkable in a government, the roads were made suit-

able for speeds considerably in excess of those usual at that

day 0

In deriving these standards crnservative assumptions

were made as to the coefficient of friction between the tires
and the road, and allowances included the fact, now pretty
certainly established, that the coefficient falls as the
speed increases. For the three classes of design, the
coefficient was taken as 0.4, 0.45, and 0.5 respectively.

By the use of the correct coefficient for the class of road
under consideration and by making an allowance for the delay
before a driver's reaction occurs, the distance necessary for
a vehicle to stop from any speed can be calculated. From the
stopping distance figure corresponding to the maximum speed
for which the road is to be designed, a minimum figure for
the radius of curvature over a convex summit can be deduced
if a suitable assumption is made as to the height of the
driver's eye above the road. Applying these principles, the
Germans calculated their sight distances to be 900 ft.,

700 ft., and 500 ft. respectively.

Were it possible to provide any degree of super-
elevation on horizontal curves, there would be no theoretical
minimum limit to the radius of curvature. But in practice,
of course, allowance must be made for vehicles traveling at
low speeds. It was therefore specified that in general the
cross fall was not to exceed 8 per cent, but where the
gradient was less than 1 per cent, it could increase to
10 per cent. These limits set the minimum radii of hori-

zontal curves. As it is well established that some part of

the centrifugal force occurring at a curve can be balanced

-27..

22‘th : beWxxbss m; fiN‘V
atomistic {saint «I to» Cask- L2 Octavian» Kass dd. 352.3% a- S

a. 2.: ‘31s

E93? of

 

-28-

by friction between the tires and the road, the assumption
was made that the safe coefficient was 10 per cent, a fiqure
which corresponds with the maximum cross fall allowable. The
minimum cross fall was set at 2 per cent. The cross iall
adopted at any particular curve depended upon the class of
Autobahn of which it formed a part, since the speed to be
provided for varied between the classes. Curves were of

such large radius that it was not thouaht necessary to
introduce them by transition, nor modify them by a widening

of the pavement. In constructing superelevated curves the
inner edge of the roadway was maintained at the general

level of the line, and the outer edge raised. The full super-
elevation was maintained throushout the curve, and the
transition was formed in the straight approaches on a gradient
of l in 200. This desifin set a limit to the minimum distance
between reverse curves, for the two ramps were not permitted
to overlap. The length of sight line required for the
designed speed was maintained on horizontal curves by the
excavation of the sides of cuts and the setting back of bridge

abutments wherever necessary.

Examination of the accompanyins drawing will
supply all the details of the cross sections of a typical
Autobahn. Standard design for any class of Autobahn called
for a four-lane divided highway composed of two, one-way
roadways each 7.5 meters wide, separated by a green strip

3.5 to 3.0 meters wide. All dimensions on the drawinq have

-29-

>\x\ TMVQKQ T MET V A§QK \Q >\%\k ,0me %%Q%u VVQNRFN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

x \Jmfi
AIIIIIIJ.NHVNIIIIIY\ .Illzm Jm1\l.lll. —l ah $M‘ I
/I mlcmz .Vuxl\ _ fil.§.\ m..-m...l\
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-50-

been converted to feet and inches for convenience of the

American reader.

Each roadway has a uniform outward cross fall of
1.5 per cent,and is flanked on each side by shoulders laid
flush with the road surface. These shoulders, which are
usually 0.4 meters wide on the inside and 1.0 meters wide on
the outside, are surfaced with bitumen to contrast strongly
with the whiteness of the concrete of which the rest of the
surface is usually constructed. On some of the last work
done on the roads, the outside width was increased to 7 feet
4 inches, apparently with the idea of providing more adequately
for emergency parking. The shoulder strips were usually about
10 inches in depth, the lower 7 inches usually being of
concrete and the upper 5 inches of asphalt. In cases where
dark-colored concrete or asphalt was used in the pavement
prOper, plain concrete was used in the top course of the

paved shoulder strip.

The concrete base for the shoulder strip was con-
structed before the pavement slab and utilized as a base upon
which to mount the rails carryinq the heavy construction
equipment used in the mixing, placing, and finishing operations.
The asphalt top was placed to the elevation of the finished

roadway after the completion of the pavement proper.

All pavement slabs were of uniform depth, 8 or 10

inches in thickness, althouch heavier sections were used

 

 

‘- - _A u a

The Munich;Salzburg Road

 

' ,' .1
0'

0n the Munich-8a zouré :u'o.:..

- 32 -

occasionally. So far as the desian of the slab itself is
concerned, practice appears to have been patterned largely
after that followed in this country, except that the Germans

did not use the thickened-edge section.

There is no curb and the ground beyond the shoulder
strip is formed flush with the shoulder strip wherever
possible. In cases of emergency therefore, there was available
to a maneuvering vehicle, not only the extra width provided
by the shoulder strip, but also the support of the around
beyond. Thus another safety factor was provided to insure a
minimum accident occurrance on the Autobahn. This outer qrass
margin is about 6 feet in width and is cont.nued as a gentle
slope to merge with the normal ground level. No drainage
ditches, as such, were formed. In general, the motor roads
were located so as to take full advartage of scenic possi-
bilities. Cut and fill slopes were rounded and were blended
in with the natural terrain so as to give a very pleasing
appearance. Careful attention was given to landscape so as
to cause as little disfigurement as possible. These,
together with adequate roadside planting, gave an appearance
of age and permanence which is quite surprising when one
realizes that the average age is only about 10 years. Notice
this feature on the typical views shown. Their basic prin-
ciple was that the natural beauty of the countryside must not
only be maintained but actually be augmented by the works, so

far as possible. Landscaping had to reqard the following

-33-

 

    

‘

  

  

I “

’ I I

Branch to Access

   

0

Road - Berlin-Stettin Route

considerations: All artificial earthworks should correspond
to the tepozraphy; roadside conditions and new planting were
based on the trees, herbs and grasses native to the district,
and botanical conditions prevailed; fully grown trees and
shrubs were preserved and used wherever possible and virgin

soil and turf were set aside and re-used.

As stated before, the new roads by-pass all towns
and villaaes and pass close to most larce cities. All were
routed in entirely new locations. There is not one level
crossing from end to end of the Autobahn. All crossings are
over and under, requiring thousands of bridges. Pedestrians
also must use bridges to cross the highways. There was no
speed limit on the roads until the American Army moved in,
and then while the war was on, MP's patrolled the highways
and even handed out tickets while German planes straffed

them. Measures were taken to prevent ribbon development and

‘3

speculation in the adjoininm lands. Advertisement displays
both upon the roads and adjoining lands were not permitted,
and no telegraph poles or structures were permitted upon or
in relation to the line of route. When the roads cut throuah
farm lands, no provision was made for the farmer to enter on
the hifihway at any point on his property. It is plain to

see that all these features enabled the motorist to travel
from one place to another with a minimum of eXpenditure on
vasoline and maintenance, and at the same time providing

him with a maximum factor of safety.

-35-

The next portion of this chapter will be spent in
enlarging upon the different types of bridtcs, crossings,
and junctions used in the construction of the Autobahn. The
bridges of the Autobahn fall into categories: those carrying
the Autobahn over natural obstacles, and bridges carrying
minor roads over the Autobahn. The standard of loading to
which-the road bridges were designed varied with the class
of road and the traffic anticipated. The maximum loading to
which the bridges were designed consisted of a 24 ton maximum
load carried on two axles, transmitting 8 and 16 tons
respectively. Reinforced concrete foot bridges span the
highways at many points where such safety measures are considered
necessary. All grade crossings havinfi been eliminated meant
an average of two structures per mile of highway. Nest of
these structures, where the length of span would permit,
were built of concrete in a variety of designs. Many
structures, particularly piers and abutments of steel super-
structures are faced with beautiful stone masonry, and all
concrete surfaces are finished in a stucco effect, and in
some cases blocked off to resemble masonry. All bridges
carrying the new highway were built with a total width of
76 ft. giving a roadway width of over 50 ft. Where steel
bridges were built almost all of the structures were

electrically welded.

The largest bridge of all, the Elbe Bridge which is

1,170 meters long, is made of reinforced concrete; but the

-36-

l v H 581;; {iii
'. a) -l\...dv::dh' $.43“

 

Figure 7
Autobahn Showing Parking Space at Left

 

Figure 9
Portal Bridge Over Berlin Ring Road

 

Figuree .
Bridge Over Breslau-Kreibau Autobahn

- 37 -

Saale Bridge at Jena, which is 751 meters long, and the
Elster Valley Bridge, which is 680 meters long, are both

built of stone.

In addition to such.large bridges as these, there
are naturally very numerous smaller bridges of which the
greater number carry minor loads over the Autobahn. The
design of these structures was standardized to a large extent
and can therefore be classed as road works. Typical designs

are shown in the group of drawings presented.

All bridges which cross Autobahns are of sufficient
span between abutments not only to require no narrowing of
the Autobahn, but also to leave an additional clearance on
each side of 2 meters to take drains and other service mains,
etc. Where the Autobahn is crossed at a curve, the abutment
is set back far enough so that the sight distance required
for safety is not shortened, just as previously mentioned in
another case. The standard clearance above the road surface
is 4.5 meters (14 ft. 9 in.) and the deck of the bridge is
usually constructed with vertical curvature on a radius Which
joins the two tangents formed by the gradients of the
approaches. Too many bridges in this country have flat decks,
causing a distinct bump when the vehicle boards and leaves

the bridge.

In the most commonly used design there is a central

support under the span rigidly connected to the superstructure,

 

 

 

 

 

 

 

 

 

 

Figure 10

KK - Most Commonly used design.
L - Used when foundation material was particularly good.

 

 

 

 

 

 

 

 

 

 

 

 

 

“: A )‘ A" I ----.-. “‘ - ,.
f Tau-uh,” * i t
'a
x _
........ iaJ M, Li. . . t T
_g§'_ -_ A ._ l._:f':_;‘: -3”... w?
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‘_2f7. _~'
.-
\ “k I J 1 '—.. o
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1*.
1’
Figure 11

M - Portal Form - only type used over Berlin Ring.
N,O - Used where more open View was desired.

 

Figure 12
Typical pedestrian Operpass.

- 39 -

which is carried on sliding bearings at the two abutments.
Reinforced concrete is the material most usually employed,
but a steel girder structure and composite steel and concrete
designs were also standardi7ed. The depth of the span was
made as small as practicable in order to *ive an appeararce
of lightness, and the sliding bearinss were frequently con-
cealed in the abutments. When the foundation material was
particularly good the design was sometimes modified. In the
modified design there were no sliding joints and the bridge
was carried by the line bearings beneath the abutments,

which were counterweighted. By this means a particularly
light appearance was achieved. In mining districts, where
subsidence was a possibility and elsewhere when the stability
of foundations was not trusted, the central support was
dispensed with and the deck was carried by steel girders
fixed at one end and sliding at the other. Bridges without
central supports were also built at points deemed to have
some special significance. The bridges over the Berlin ring
road, for instance, all have the portal form. On curves or
in other situations Where it was desirable to give a more
open View, the abutments were not made solid, and the bridge
consecuently had four openings. But this design offered the
disadvantage that if the crossing is an oblique one there is
difficulty in finding room for sliding bearings on the

narrow supports and an arrangement with flexible concrete
pillars as intermediate supports and fixed and sliding bearings

at the abutments was sometimes adopted. For deep cuts arch

-40-

forms were standardized.

Where the Autobahn passes over a secondary road
the bridge was constructed in much the same manner as the
more simple of the overbridges, but on account of the lesser

width there was no central support.

A reference to the map shows that at numerous
places there are junctions between the new roads. In
addition, it is necessary to allow access to the Autobahn
from the ordinary roads of the country. In order, however,
not to interfere with the maintenance of high-speed traffic
flow the number of access points was strictly limited only to
the more important ordinary roads and the distance between
access points is as much as 10 miles to 15 miles. All other

roads are carried under or over an Autobahn without any

connection with it.

In no other country, with the exception of the
United States, has the problem of the design of road junctions
to suit high road speeds been so carefully considered as it
was in Germany. The road junctions were designed with three
primary thoughts in mind: First, the highest degree of
safety; second, a lay-out that will be quickly self-explanatory
to the motorist; and third, the maintenance of a continuous

flow without collision points or traffic intersections.

The types of junctions may be broadly divided into

three types: access from ordinary roads, bifurcations of an

-41-

     

D swam w.

 

 

 

,_ fl cwvtnu'u' 00039!“ J muawr MSW“:

Figure 12A
The types of crossings and junctions used.

    
  

 

 

   

L
[3; .n -‘v-:. - .1 ..'.-::.:'...i.'.:.:.": '
1.

7—1 .4 |

‘ J0 L A mumr Arms , x
' ' 500 9
§

 

 

 

 

 

 

 

 

 

 

MUHLSIDID M‘CISS

Figure 128
Two types of accesses used..

Autobahn, and the crossing of two Autobahns. The first
mentioned may be further subdivided into cases where the
ordinary road continues over and beyond the Autobahn and
cases where it joins the Autobahn and continues no further.
All types of bridges and junctions mentioned herein are
illustrated on the drawings included and should be referred

to by the reader when ever the description is not clear.

The chief interest lies in the arrangement at the
points where the feeder roads from each side join the Auto-
bahn. It will be observed that the "mouth" of each feeder
road is divided by a triangular island, and that there is a
grass-grown strip, 2 meters wide, separating the Autobahn
from the access road. Vehicles entering the Autobahn travel
for 100 meters (528 feet) on a lane behind this strip parallel
with the main roadway and are thereby enabled to gather speed
before intermixing with the traffic upon it. In a similar
way vehicles leaving the Autobahn must be given space in which
to reduce speed; but in order to allow mistakes to be rectified
and because a vehicle traveling fast needs more room, no grass
strip intervenes on this side between the lane and the roadway.
A connecting lane between those for entrance and exit allows
a driver who has mistakenly turned out of the main roadway to
regain it without reversal. Use was sometimes made of the
triangular island by sitting a aasoline station on it. It
should be noticed that vehicles leaving the Autobahn are not

required to negotiate curves of less than 50 meters (164 ft.)

-43..

radius, but that entering vehicles, on one side, are given a
curve of 25 meters (82 ft.) radius. Gradients generally are
no greater than 4 per cent. The one-sided access design

has been called the trumpet junction on account of a fancied
resemblance to that instrument. When roads of lesser
importance joined an Autobahn similar access structures were
used, but the curves are more severe and the gradients
steeper. Occasionally, where the distance between access
points would otherwise have become unduly long, it was necessary
to allow comparatively minor roads to join the Autobahn. In
these cases the structure was mdch simplified, and the green
strip and triangular island were omitted. Curvature and
gradient are similar to those adopted for the less important

”accesses.

When an Autobahn bifurcates, the deSign adopted
was usually a modified form of the trumpet structure, with
less steep gradients and larder radii of curvature. This
arrangement is narticularly suitable when traffic to and
from the "stem" of the ”Y" predominates, and when there is
little traffic between the two arms. But when the traffic
is more or less eiual in all direct ons, the sharp turn at
50 m. radius required to be taken by traffic in one direction
across the arms is a disadvantage. Near Mannheim, therefore,
where the three branches lead to Frankfurt, Heidelberg, and
Mannheim respectively, the triancular structure was preferred.

On account of a future branch from the Heidelberg road to

- 44 -

“5.?a - fi' 1‘, d" i 5.. I- v;
_ . ‘ , ‘ ‘e - ‘ D . . ‘ o I
i‘\ I ‘.- "h “5‘s? -' ’s} C vix ". '. 3 ~~~ * ' -'- -

The HannheimsFrankfurt-Heidelberg Triangle

 

 

 

Figure 12D -.
An Autobahn grade separation

 

Figure 123‘. .
An access system to the Butobahn

-45-

Karlsrube, that was contemplated, the lesser curvatures were
given to the Frankfurt-heidelberg and hanrheim-heidelberg
connections. The disadvantages of this solution to the
problem of the bifurcation are the large area required and
the three bridge crossinas, all at somewhat acute antles. It

is therefore expensive, and only used at this one point.

The four-leaf clover separation was generally
reserved for the crossing of one Autobahn with another. This
design was used at Schkenditz near Leipzig and at Hermsdorf in
Thurinqia. Through traffic is unhindered, but turnina traffic
is recuired to negotiate curves of 50 meters radius. Another
solution to the crossing of two Autobahns is the Roundabout.
This design was used at Leverkusen, at the crossing of the
Cologne-Dusseldorf and Dortmund-Aachen highways. The rounda-
bout scheme has the advantages over the four-leaf clover that
all curves within the area have the same radius, 100 meters,
and that drivers get a clearer idea of the arrangement when
approaching it, especially if the ring road is elevated above
the two crossing highways. It has, lowever, the disadvantage

that interweaving of the traffic is necessary at four points

on the ring road.

The system of road signals devised for the control
and information of traffic on the Autobahn is simple, clear
and positive. The danger Sign, as such, is non-existant,
because of the absence of danger features in the design.

Only in certain forest districts is a form of hanger

-45..

sign located. These are to warn the driver of the possible

movement of game across the road.

The signs that exist can be classified as follows:
First, directional with distances; second, gasoline stations,
with distances; third, parking; and forth, distance to the

next junction.

The question of illumination of the expressways
was one for debate. Two systems were put into effect at
different places and an attempt made to determine which
was best from all standpoints. The first was a direct
lighting system -- that is, stationary lamps at various
places along the road. Different types of lamps were used,
but no one was employed on the whole road system. The
second was illumination given by the vehicles themselves.
As an aid for this type of illumination, reflectors were
placed alongside the road, very similar to those used here
in Michisan. Furthermore, bushes were planted in groups,
and only species were used that would readily reflect the
light from the autos. Thus at night the visibility was
improved and during the day the landscape took on a more
varied appearance. Moreover, the bushes made the road a
separate unit that could be entered only at especially
constructed entrances. From the standpoint of the psychology
of the driver, the bushes were not of only one variety, but

were so chosen and arranged as to break the monotony of a

long trip. The hedges did not allow snow to pile up and block

- 47 -

traffic, because they were not planted in a continuous line.

At various intervals on t a grass strip in the
middle of the highway, hedges were planted at right angles
to the direction of the road. These hedges were slightly
higher than the lights on the vehicles, so that the lights
from automobiles moving toward each other did not blind the
drivers. The arrangement of such hedges is especially
important at curves, where the liqhts of the cars that are
traveling in the inner lanes of the curve, shine directly
into the windshield of the cars cominq from the other
direction. In addition to preventing the light from one
side of the road distracting drivers on the other side, the
hedges served the purpose of outlining the direction of the
road by reflecting the light of the individual autos. The
main disadvantage of these hedges is that where the road
falls and rises perceptibly, the light shines over the hedges

and thus defeats their purpose.

In regions where there is particularly heavy
snowfall, as in East Prussia and the Bavarian Fountains, the
highways are built on embankments to prevent the snow from
accumulating on them. In the mountains the roads very often
are one-way roads; that is, those ascending are in a different

location from those descending. This was done from the point

of view that conditions favorable for driving upward differ
from those favorable for driving downward. Furthermore, from
the standpoint of lardscape beauty, such an arrangement is

very often the best.
- 48 -

If the reader will permit the injection of a
personal incident at this point, I would like to relate an
experience my father had while he visited Germany in 1938.'

He used the Autobahns extensively during his stay, but it was
some time before he became accustomed to the systems of access,
for very few such structures had been built in this country
before 1958. Cn one occasion an improper turn brouaht him on
the wrong lane leading in the wronq direction. Expecting to

'V.

find a cross-over a short istance up the road, he drove in
search of one. All he found, however, was an occasional sign
stating that the spaces between the hedges on the grass strips
were not to be used as cross-overs. Also a police patrol
station was encountered about every two miles. These police
were not ecuipped with squad cars, but merely with telephones.
The patrol stations were close enough together that a call
reporting a violator to the next station was sufficient to
stop that driver. If a waving policeman failed to stop him,
road blocks were set up at later stations. After my father
had driven over 10 miles without finding a cross-over, he
decided to take a chance on crossinc the grass strip. He

made the crossing mid-way between two patrol stations, hoping
he would not be seen. But the policemen were alert, and he
was stopped at the first station. Since he was American, had
an American car with a Nichigan license, and convinced the
policeman he could not read German, he was released with a

warning. This gives you an idea of how far you can travel

on a road of this type before you can turn.

-49-

There were many services on the roads offered to
the Autohchn traveler. They included service stations,
garages, refreshment stands, and tourist camps. These were
all built and administered by the state and all were strictly

modern and equipped with all modern conveniences.

To summarize the impressions of all those who have
traveled on the Autobahn: The foremost and the most lasting
impression is the sense of safety and security regardless of
the high speeds at which traffic travels; the absence of
monotony, linked up to the aesthetic duality of the results
achieved; and the marked absence of any feature arising from
the work which would cause disfigurement or destroy the beauty
of the countryside. Apart from the speed and duality of the
construction, the design made provision for a traffic growth
well in advance of requirements, and the scale of the work and
standards of design opened a new era in the conception and

engineering of public highways.

-50..

CHA TER V

CONSTRUCTICN F?CGRESS FADE END fiiTERIdLS UbED

Naturally, the buildinq of the Autobahn was known
of throushout the world, and since the materials used were
supposed to be the best obtainable, experts from all over the
world came to investigate. So areat was the interest in the
highway building program that s ecfial arrancements were
necessary for handling the engineers and other visitors who
called at the office of the Insoector-General of Roads in
Berlin. The office records showed that practically every
country in the world had sent technical advisers to Germany
to acquaint themselves with the development. There was out-
standing interest in observini what conld be accomplished
when a far-flung highway procram could go forward without any
decentralization of control and under conditions where

influence on the selection of r ute was disreqarded if it

(D

hampered th attainment of broad objectives.

This chapter will tell of the prosress those
visitors found during their visits throuahout the construction,

and also of the materials that were used in that construction.

On September 7, 1954, Dr. Todt announced that work
on the new highways had bequn in fifty-one places and that
52,000 men were employed on oinstruction work while another
100,000 found jobs producinm the materials used. By October,

1954, some 1,500 kilometers (about 900 miles) were already

in hand. The first section required over eight months to
complete, for it was May 19, 1955, when it was opened in the
presence of Hitler and numerous government officials. This

first section ran fourteen miles from Frankfort to Darmstadt.

By the end of 1954 there were about 80,000 men
directly employed on the works, and in 1957 men employed
(including structures and material supply) were stated to be
over 250,000. The work in all cases was executed by
contractors, but in some cases, owing to the remote position
of the work, about 20,000 men lived in workers' camps, and
each camp was under the control of a leader. These camps

will be described in the next chapter.

By September 1, 1956, a total of 750 miles of road
had been completed and 650 were open to traffic. The Reichs-
autobahnen had fulfilled their primary aim of reducing employ-
ment, so that in 1957 when labor and materials were becoming
scarce, the policy was chanced. No longer were operations
organized to use a‘maximum of manual labor. The labor employed
per mile fell off considerably because of the increasing use
of machinery. Although the total number of workers, including
auxillary employment in the production of materials, rose as
high as 250,000, as mentioned before, the number employed
varied seasonally. From the time the roads were begun in
September, 1955, to September, 1957, the number of hours
worked was 82 millions. The maximum number were at work on

the project in 1956 when 124,000 earned their pay checks by

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working directly on the roads. In 1954 there were 84,000
so employed and in 1955 over 115,000. The use of machinery
made its mark on the fisures in 1957 when the maximum number

employed at any one time was 101,000.

Those 82 million hours of work did not show as
many miles of completed road as one might expect. By
September, 1957, 1555 kilometers (960 miles) of the new roads
were open to traffic, and some 1650 kilometers (about 1000
miles) were under construction. In the w rk up to that date
only 597,000 tones of iron and steel had been used, as compared
with three million tons of cement, which was about 123 of the
total national output. Vast quantities of stone, rand,
pebbles and earth had been used, and the carriage of materials
for the motor roads was officially mentioned as one reason
for the rapid expansion of goods traffic on the railways which
occurred in 1957. It was probably also one cause of the
shortage of goods wagons in the coal and iron centers of west
Germany. With less than three years of work done on the roads

up to May, 1956, over 550 million dollars had been spent.

Progress continued at the approximate rate of 500
to 600 miles per year after the who program really got rolling.
The first years did not yield that average for only 1200 miles
were completed at the and of 1957. On September 28, 1956,
Hitler dedicated the first 1000 kilometers (about 690 miles)
of Autobahn with a spefich in wtich he emphasized tnat Germany

must make herself independent of "the good or ill will of

-53-

sources 1ving outside Germany.... The automobile roads,

Jitler said were heips built for all eternity for the German

7
people whom he pictured as ridinn in automobiles as readily

as the peOple of the United States.

v

On April 7, 1958, Chancellor Hitler broke o-'round
near the frontier town of Jals for the first Austro-German
automobile road. This road c nnected the two large and

famous cities of Vienna and Funich, and made the trip

few hours.

between only a matter of e

The world said Germany was crazy when they saw
Germany's motor speedway business report for 1955. With
5055 kilometers (1900 miles) completed by the end of that
year, the cost had been 1,000,000 marks per kilometer.
Since the road was not half finished accordinq to the
criminal plan, many thoumht there was considerable cause
for concern. But they had not seen anythinq yet.‘hr Germany
was preparing for war and wanted as many of the roads comploted
as possible. Therefore the expenditure for 1959 was 153,000,000
marks more than it was in 1958. Construction costs proper in
1959 amounted to 921,500,000 marks, with continfent expenditures

set at 199,500,000 marks, making a total of 1,120,500,000 marks.

d? Very little construction was done after the start of
the war, but enouqh of the roads hrd been completed to provide
an efficient arterial system 5,000 miles long which could
accommodate the transportation of troops at:the rate of 500 and

artillery at the rate of 200 miles per dav.

-54..

The material, especially the cement used in the
construction of the Autobahn, was considered by most Americans
to be inferior to materials used 'ere, as judged by American
strndards. However, judging from the condition the pavement
is in, it may yet be seen that their materials were not so
inferior after all. Mr. M. A. Swayze, who made a trip to
Germany in 1945 specifically to study the cement industry,
reports as follows: "The areat majority of tke plants visited
were making a product which was inferior in practically every
way to the cements manufactured in the United States or in
Great Britain. Their control of raw mix proportions was
generally lax, and fine grinding of these materials which we
believe essential for good Quality was nowhere near that of
American practice. The burfing operation is much lighter than
ours, even in plants with modern kilns, and free lime contents

as high as 2.5 percent are not uncommon."

Mr. Swayze's appraisal was, of course, based on
observations of conditions in 1945. To just wh t extent
economic donditions, particularly an acute fuel Siortage, may
have tended to lower postwar manufacturing standards as
compared with those in effect during the thirties, cannot be
stated definitely. Furthermore, the cem nts used in the
construction of the motor roads were supposed to meet special
requirements for flexural strength, dryina shrinkage, and
fineness which were not imposed in the case of the ordinary

product. Even so, it seems probable t.at even these specially

-55-

selected cements were quite inferior, when judged by our
standards, to modern American cements. For example, Swayze's
survey indicated that, entirely aside from the matter of fuel
economy, the methods for controlling uniformity of product,
such as facilities for storing and handlinq clinker, pronor-
tioning materials including the gypsum, etc., were very crude
as compared to modern American practice. This conclusion
would, of course, apply as well to the prewar German ce ent

as to the postwar product.

The Autobahn cem nts were undoubtedly somewhat
coarser than our present-day American cements. The Germans
required that between 5 and 25 nercert be retained on a sieve
having 178 openings per inch. Compare this with the modern
American cement, which rarely will have more than 5 or 4
percent retained on the standard No. 200 sieve (200 openings
per inch). Particle-size distribution in the typical auto-
bahn cement was also probably ruite different. According to
Swayze, practically all finish grinding in German cement mills
is by open circuit as compared with our modern closed-circuit
Operation used air separators. In open-circuit qrindins, the
final cement product contains the various sizes just as
produced in one continuous passage throueh the grinding mills.
In closed-circuit arindine, the various sires are classified
by means of air separators and the coarser particles are

returned to the mills for further grinding.

It is probable also that the German cements were not

-55-

as hard burned as our modern cements. Apparently the only
requirement for soundness was a 2-hour boilin: test. The
autoclave test has never been used. According to the best
technical thouaht in this country, an autoclave test is
absolutely essential for the proper control of soundness.

Many failures in the United states, particularly in the
southeast, have been attributed to the absence of an auto-
clave requirement in specifications, and it will be interest-
ing to note when discussing the present condition of the auto-
bahnen that such a requirement has never been used by the

Germans.

Cements for concrete road construction were selected
from the commercially available products, on the basis of the

following characteristics:

1. Rich flexural strensth.

2. Moderately hieh compressive strength.
5. Low drying shrinkage.

4. Toderately coarse arind.

In addition, as mentioned above, all cements were
required to pass a 2-hour boiling test for soundness. This
was a field control test for uniformity during manufacture,
the other tests beina used primarily as predualification

tests to determine the acceptability of a particular source.

In addition to straight portland cement, the Germans
recognized two types of portland-blast-furnace slam cement:
Eisenportland, containinq about 70 percent portland cement

and 50 percent blast-furnace slag, and Hochofen cement,

-57..

containinz about 15 percent portland cem—nt and 85 percent

blast-furnace slav. Because of its slow hardening character-

1.].

istics, the Fochofen cement was not used to any extent n
road work. The Eiserportland, however, was used euite exten-
sively, particularly in northern Germany. The manufacture of
this type was, of course, limited to those plants sufficiently
close to the blast furnaces to make the utilisation of the

slag economically justifiable. The availability of almost
unlimited cuantities of slap, together with the Great saving
in fuel, nade the msrrfacture of Eisenportlsnd very attractive;

and it is understood that in the neichborhood of one-third of

the entire mileaqe of rotor roads ccntains this type of cement.

The instructions somerning the selection, processing,
and control of aagreeates for concrete pavement construction -
were such as to insure excellent results from the standpoint
both of the duality of the hardened concrete and the uniform-
ity of the consistency of the mixture as it was placed.
Asnreqate quality was insured throush the use of compressive
strenqth and wear tests in the case of crushed rock and wear
tests in the case of Gravel. Ferd rocks, such as qranite,
basalt, and quartzite, were preferred. Durability was
judged apparently on the basis of experience, as the record
does not indicate that laboratory tests for soundness were
used. Blast-furnace slaw was permitted but it was not used
to any extent. The requirements for blast-furnace slag were

stated to be about the same as for crushed rock. Considerable

-58-

attention was paid to the matter of impurities, and freedom
from flat and elonaated particles was insured by requiriny
that the breadth of an individual particle should be not less
than 65 percent of its lenqth and that its thickness should

be not less than 25 percent of its lenyth.

In the matter of separated sizes, derman practice
differed markedly fromthat employed in this country in that
it was apparently the universal practice to recuire that the
sand or fine aefrefiate be furnished in at least two fractions,
0-0.12 inch and 0.12-0.28 inch. To insure better control of
grading, the material below 0.12 inch was sometimes still
further separated into two or three sizes. It is obvious
that with so many separations, very close control of the total

fine segregate grading could be obtained.

For the larger sizes, the separations were usually
0.28—0.59 inch and 0.59-l.18 inches. These were the size
separations for the top course. In two-course construction,
a somewhat larger (1.58—1.97 inches) maximum sive was used

for the bottom course.

Most of the pavements on the autobahnen were
constructed in two courses. This was necessary not only
because of the difficulty of p operly compacting a single
course of very dry concrete 8 to lo inches in depth, but
also because this type of construction made it possible to
use a somewhat inferior type of aqqresate in the lower course --

a matter of considerable economic importafce in some instances.

-59-

It was the General practice to desian all paving
mixes in the laboratory prior to construction, using the
same cement and asgrecates to be furnished later to the job.
The basis of the design was the develOpment of a mix that
would have sufficient workability for placing and finishing
with the eouipment to be used on the work, and result in
concrete conforming to the following requirements for strength
at 28 days, usina a cement content of not less than 1.55
barrels per cubic yard and not more than 1.57 barrels per

cubic yard:

Flexural Strength: Lbs. per sq. in.
I‘flinimm . o o o o o . g o o . o o o g 54:0
Average . . . . . . . . . . . . . . . 640

Compressive Strength:

“Zinimllm O O o o o o o o O o o o o o o 4 ’ 700
Average 0 o o o o o o o o o o o o o o 5 g .700

It was further provided that the strengths at 7 days
should not be less than 70 percent of the above values. It
was the practice also to check the strength design by mvans of
tests of compression and flexure specimens made during con-
struction and by means of tests on cores made at the age of

approximately 60 days.

The amount of mixing water was not specified directly
but was indicated as the minimum required for the chosen method
of placing. For the zero-slump concrete which seems to have
been used normally, a water-cement ratio between 0.55 and

0.50, by weight, was specified. A somewhat higher water-cement

-60-

ratio was permitted when the concrete contained crushed stone

than "hen aravel was used.

These specifications on materials should show the
reader that much care was taken to insure that the road would
last, even if their requirements were not as high nor as rigid

as those in this country.

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CHAPTER VI

SPECIFICATIONS AND CCNSTRUCTIGN KETHCDS

There were many differences between Germany's
design and construction methods as compared to those here and
in Canada. There were several reasons for the variations,
the most important of which was the personal ideas and
eccentricities of the German engineers. Other reasons were
the necessity for chances due to climatic conditions, sub-
soil conditions, etc. The German enqineers decided exactly
what they wanted and proceeded to lay plans for securing it.
All machinery, etc., was designed to fit the construction of
the kind of pavement they required. Routes were laid, land
acquired, etc., and the roads built exactly along those lines,
without any deviation or compromise. This chapter is dedicated
to the construction methods used and the specifications that

lead to be followed in that construction.

When the work was begun a difficulty was encountered
in teat many of the men enrolled for the construction of the
roads had, as a result of years of unemployment, forgotten
their skill. Moreover, owing to that lack of political unity
which has already been mentioned, every district and town had
wages fixed by itself without any particular reference to
these existing elsewhere. Very soon after the work was begun
it was found essential to eliminate such.waee differences,
and a system of standard wages was formulated. The distress

of the unemployed was so great in 1955, when the Autobahnen

-52..

Company was formed, that it was decided to besin work in as
many different localities as possible in order to benefit a
larae number of workers. The result wos, as seen from the
map in Chapter IV, that many gaps in the system exist.

These gaps were much larger {nd more plentiful during the
construction. In 1957 with about 800 miles of road completed,
the longest route open was from Hanover to the uncompleted

Berlin rins, a distance of about 150 miles.

Contrary to the general belief at that time, and
even now, highway construction in Germany was not carried
on by forced labor, but all was let on contrcct. To
accomodate the workers, many of whom were livinq at some
distance from their homes, camps were built. The buildings
were of timber and were desisned to be portable. They were
usually arranaed around a square and a camp venerally
consisted of twelve dwrmitories for eighteen men each, a
social or livins room, a kitchen and bathrooms. The admin-
istration of each camp was left larsely in the hands of the
men themselves. The outfitting of the camps was under the
control of the Insnector-General. Mr. Walter L. Sanders,
district enfineer at Ottawa for the Ontario Department of
Hig-ways, visited the construction camps in 1957. He said
that conditions were an eye-opener to him and the specifi-
cations demanded were extremely hiq . The men living in
camps had accomodations as good as in a hotel. There were

even bedspreads on the cots, he said. The men were well

paid and married men workinc on road jobs received extra

-65-

,ay as separation allowance.

Previous failures in road construction have often
been due to an insufficient study of subsoil and foundation
conditions. Attention has always been Niven primarily to
surfacing, reqardless of the ever-increasing weight of motor
cars and trucks. The subsoil under the road surface is,
however, as important as the foundation under any other
enoireering work and the German ensineers recognized this
fact. A thorough investication of soil and sub-grade
conditions formed a major part of the routine of German
motor road construction. It was emphasized that such investi-
gation should take place at a sufficiently early staae to
influence, if necessary, the choice of alicnment. Whenever
possible, bad subsoils were bypassed. Where such areas could
not be avoided, detailed investigation was carried out to
determine the magnitude of the settlement of soft undersoils
due to loading, the time required for such settlements to
occur, and the most economical height, and slope of embankments.
When it was necessary to place high embankments over yielding
subsoils, the completion of the earthwork was planned so as
to permit the major portion of the settlement to take place
before the concrete slab was placed. The course of the
settlement was accelerated throuah lateral diSplacement of the

subsoil by overloading or by blastin".

On each section, the first field work consisted of

testing, dissing and drilling, and studying excavation and

-64-

soil from the neighborhood. The field laboratory test of
subsoil of the highway controlled all processes from the
beginning of construction. In addition to direct testing,
the indirect dynamic testing was also used. This process
consists of a vibrating machine sendins out waves to the

soil to be tested, while a seismoqraph indicates the oscilla-
tions at various distances from the center of vibration.

From the speed with which the waves pass throush the soil,

conclusions can be drawn as to the nature of the subsoil.

The soils of Germa y vary from cohesionless sands
to plastic silty clays and clays. Most of the silty clays
were of such nature as to reduire careful moisture control
for adequate compaction. Such soils would be subject to
frost heave under adverse drainage conditions, and pumping
at joints would occur on them if free water entered expansion
joints or cracks and if a sufficient number of heavy loads
passed over the pavement. The practice of placing a layer of
granular material under the pavement was, no doubt, a

contributing factor in the prevention of pumping in such

08.888 0

A modern soil technique was employed in the first
stage by means of a soil survey alone the line of tentative
route. The soil samples were taken and forwarded to the
central laboratory and analysed for the determination of the
special steps which might be necessary to ensure maximum

consolidation and maximum stability. Only after the work

had passed the standards imposed,was actual construction

of the roadway authorized.

Soils were classified as follows: (a) top soil,
(b) non-cohesive soil, (c) cohesive soil, (d) stone
(e) waterlogged soil (peat, ooze, etc.). The different types
of soil were removed separately and drainage facilities were
reeuired. The material used in the construction of embank-
ments was placed in successive layers, the soil being tipped
from above and then distributed to the correct level. A
portable apparatus for measuring the height of each layer as
it was constructed was devised. Consolifiation was.effected
by mechanical means. The weight of the tamping machines
used depended upon the gauge of the rails used for the trans-
port of material. Liaht models were used on the shoulders,
which were consolidated first, from tBe edges toward the
center of the embankment. If any spreading occurred at the
foot the extruded material was used in finishing at the toe
of the embankment. Irregularities in the upper surface of the
embankment were eliminated by light rollini. The soil con-
stituting the foundation of low embankments was required to
be homogeneous; intrusive deposits were removed and replaced
by appropriate material. No settlement was supposed to take
place on such a foundation provided the embankment was well
consolidated. On weak foundations the amount of settlement

to be expected was calculated and taken into account.

Layers of peat up to 15 ft. were removed and replaced

-55-

by sand. If the water content of the peat was not too high,
drainage channels were cut in the subsoil and filled with
subsoil material. It was found that if the height of the
embankment was considerable and thorough consolidation was
effected by machinery very little settlement took place
after construction was finished. Where excessive peat was
encountered it was removed by blasting and replaced with

stable material.

Special attention was paid to the uses of fertile
top soil for encouraging material growth on slopes, and
existing vegetation was carefully protected. Where the
formation consisted of stcne, care was taken to make it
smooth and all projecting material was removed. Cracks were
filled with non-capillary soil. Where too much rock had been
blasted the formation was leveled by applications of lean
concrete. Embankments of hard rock were constructed in
successive courses. Soft rock was consolidated with heavy
tamping machinery. Where other types of soil were placed

on a foundation of stone an intermediate filter course was

provided.

Special care was exercised in the selection of the
soil uced in hack-filling engineering structures and consolid-
ation was effected with tamping units weighing up to 1,100
pounds. Hand tamping was not permitted. A sritable drainage

system mpg peruired here also. Drainage cherrels were laid

under the road bed itself and any ditches recessary for

-67..

drainaee during construction were subseruently filled. Store-
filled drains were provided with a filter course in order to

prevent entry of embankment material.

The following recompendations that were made concern-
ing the foundations, earthworks, and drainage of the road,

were taken directly from PUPIIC WORKS for December, 1936:

"(1) The choice of surfacinq must depend larfiely
on the nature of the suborade; surfacinjs of the "flexible"
type should be constructed on stable subarades oan. Concrete
surfacinys have oiven satisfactory service on unstable sub-
grades, but aderuately dowelled ioints must be provided.

"(2) Concrete foundations are recommended on sub-
grades waich are liable to frost dawnse. Foundations of
stone pitchina require special protective mecsures; surface
rep irs effect no permanent improvement when such foundations

ve banme displaced either in the later staqes of construction,

(03

h
under traffic, or by frost.

"(5) In soils where the proportion of particles of
less than 0.0? mm. diameter does not exceed 3 per cent, frost
damaae does not take place. If the particle si7e is very
uniform, the safe proportion of such particles may be as hish
as 10 per cent.

"(4) Weasures of protection adainst frost include
the provision of a lover of porous material (gravel, sand,
brushwood), or of a bituminous insulatina layer.

"(5) All types of soil, with the exception of soils

-68-

containinq a high proportion of orsanic matter (e.a., peat),

can be successfully used in the construction of embankments.
The consolidation of plastic soils, however, must not be
undertaken in wet weataer, as tampinq then increases the
plasticity of the material by incorporating a further ouantity
of water.

”(5) Tamping or vibration is preferable to in-
undation methods, though these may be successfully combined
with either of the former.

”(7) In cases where a considerable proportion of
plastic material must be used, greater stability is obtained
by placina and thorouahly consolidating alternate layers of
plastic and porous soil. The stabilization of such a core
is exceedinzly gradual, and there is constant liability to
spread or subside.

"(8) The mixture of clay or loam with sand or
gravel is not successful in practice, as a comparatively
small amount of clay dangerously increases the plasticity of
the mixture.

"(9) Caref l and uniform consolidation is of first
importance. The depth of soil to be placed and consolidated
at a time should in no case exceed 40 in.; the usual maximum
is 50 in. In the case of backfills in the construction of
abutments the soil should be placed and consolidated with
light achinery in layers not exceeding 8 in. thick, in order
to avoid damaae to the adjacent structures. The provision

of a dry masonry course behind wine we ls of abutments is

-69-

actually injurious, as the soil of the fill becomes forced
into the interstices of the stone and thus permits subsidence.

"(10) The generally accepted limitinq slope for
embankments (l:l%) and excavations (1:2) is too steep for
plastic soils.

"(11) Drainage courses constructed on the face of
embanked or excavated slopes assist surface drainaqe only;
they are without influence on the shear resistance of the
interior, and hence cannot prevent spreading.

"(12) Side ditches are usually superfluous except
where they are re uired for the drainage of adjacent land;
in most cases they suffice for the removal of surface water
only, and this can be more economically effected by means of
channels or percolation courses. The latter, which must be
of sufficient depth, afford the best means of eliminating
ground water or the interior drainage of embanked or excavated
slopes.

”(15) The culverts, etc., should be laid in a
course of porous material which widens considerably towards
the upper surface; this procedure eliminates the irregular
incidence of frost action above the culvert, and hence minimizes
possible injury to the surfacing during frost.

"(14) Blasting is the most economical method of

removing peat strata of considerable depth."

Notice that in the design of the earthwork, dander

from frost damage was given special attention. Soils which

-70-

contained more than 3 percent of particles smaller than 0.02
millimeter were classified as subject to damaoe by frost
either by heaving or by softening. It ”as recosnized that
water must be able to reach the frost zone by capillarity
before frost damage could occur, and if the ground-water
surface was at a qreater distance below the frost zone than
the capillary rise in the soil, no frost damaqe would result
provided there was no entrance of water from the shoulders
or side lepes. Efforts were made to avoid frost dcwade by

the following means:
1. Placiro the concrete sloh a sufficient heicht
above ground water to avoid saturation by capillarity, or
lowering: the ground-water table by drainage.

2. Replacement of s ils susceptible to frost
danase with soils not susceptible to such damase.

3. Use of layers of coarse Granular material or

of impervinws strata such as bituminous concrete slabs, to

prevent capillary rise of orouna water.

J.

The followinv statement, from a publication
entitled ”Guidinc Principles for Doadyay Qlahs" issued for
the use of endineers encased in the desien and construction

of the Autohahn, illustrates the importance placed on investi-

CD

cation of poss hle frost dens: : "The prevention of frost

damage must in every sindle case be exhaustively investi“ated

according to terrain and chance in soil, and may not be

handled in a routine manner."

-71..

In areas where around water was found to flow
toward the road, it was intercepted by lonmitudinal drains.
Drains were also used to lower the around-water elevation
under the roadway when such a procedure was considered

effective and economical.

In a great majority of the mileage, the concrete
slab was placed on embankment. In flat terrain the grade
line was raised 5 feet or more above the natural ground level,
and in cuts the roadway was excavated below grade and back-
filled with selected material. This procedure provided good

mplified snow removal.

'r—Jo

drainame and in the open plains s

Cohesionless sand was used in fills wherever it
was available. Sand was hauled long distances to avoid the
disturbance of farm lands that would result from taking
borrow with a shorter haul. When sand was not available for
the entire embankment, it was used in the top 8 to 32 inches.
A thickness of 8 inches was most common. The sand was placed

the full width of the grade in fill sections.

Where sand for the entire fill was not available,
relatively thin layers of srsnular material were placed at

several elevations and to the full width of the embankment.

Embankment slopes were made steep (usually 1%:1 or
steeper) to reduce to a minimum any encroachment on farm land,
and embankment slopes were protected aoainst the entrance of

moisture by soddinq immediately after completion. In some

-72-

instances a full-width layer of granular material was placed
in the bottom of embankments composed of cohesive soil, to

aid in the drainage.

Cohesionless sands were compacted with a rammer
called a "jumping frog.” The device was actuated by
explosions of gasoline in a cylinder and the explosions
were controlled by a manually operated snark. The weights
of the ”frogs” for embankments varied from % to 1 ton and
for the area under the paved shoulder a machine neithing

800 pounds was used.

1

Cohesive soils (silty clays eno clays) were compacted
with smooth-face and sheepsfoot rollers. The thickness of
each layer of soil before rolling was approximately 18 inches.
field laboratory was maintained on each project where
cohesive soil was used, and the moisture and density of the
soil were carefully controlled. Very little effort was made
to compact sand or cohesive soil back of bridne abutments and,
as a result, there are many settlements in the approaches to
bridges. That such settlements were anticipated is evidenced
by the fact that stone setts were placed adjacent to many
bridges so that fill settlement could be corrected conveniently.
The setts were arranaed in a fanlike pattern similar to that

of

employed in the case Durax block in this country.

Over 95 per cent of the roads were constructed of

Portland Cement. Possibly one of the main reasons why the

-73-

 

Figure 12F"
Tamoing machinery

 

F1 gure 12G
"Jumping Frog" used to compact cohesionless sand.

-74..

Germans decided on Portland Cement concrete for their new
roads was an economic one. Cement plants are scattered all
over the country, and therefore its production was entirely

a domestic watter. However, the specifications for the
cement were high as shown in Chapter V and only about one-
third of the manufacturers could meet the requirements.

Since ample supplies of material were available, the specifi-
cations were maintained. Coarse and fine aqdregates were
carefully selected. For fines, two grades of sand were
usually specified. There were three, four or five gradinis
of coarse aesreqate. With bins and weishing equipment for
each of the seven sizes, a batch readv for the mixer was made
up of a specified amount of each of these seven accreoates.
The cost of this careful Gradinq was considerable, and there
was doubt in many minds as to whether such refinement was
justified by the son what better results. It is true that
consistently high-strength was obtained -- around 5,800 lb.
per sq. in. compressive strensth, but this was due 1 rgely to
the wreat reduction in the water content. In work done here
With accurate water control and using a plastic mix of about
one inch slump, strenqths of about 5,000 lbs. at 28 days are

easily obtainable, and the duality of this concrete has been

good.

We have covered the soil research that was done
prior to the laying of the road, and also all other eartework

snecifications that existed. Now let us follow the laying of

-75-

the road from the excavation to the final curing. Excavated
material was deposited in layers of 1 ft. 6 in. to 5 ft. 6 in.,
and consolidation of filled around vas carried out either by

a 2% ton drop hammer or by a consolidatint machine in which
four hammers operated side-bv-side. The formation of the
subérade was made with a spreader, or levelin“ beam, and
compacted by a tampina beam which followed. The beams covered
the full width of the roadway. The tampind force used was
approximately 5 tons ner souane foot. The specifications

he earthwork to be formed within an accuracy of

(it

called for

2 inches. mhe sand cushion base was then placed, usually to
a depth of about 6 inches, and the final leveling of this

foundation was reouired to be accurate within one-half inch.

When the construction beaan, extreme practices
were used. The complete pavement then consisted of 5 to 4
inches of dravel spread on a suhQrade, 5 inches of porous
lean concrete, a 8 inch course of averace Grade concrete,
followed by a 3 inch course of excellent Trade concrete, with
a wire mesh between the last two courses. Later, this
procedure was modified, and the pavement consisted of a 6
inch sand cushion on the subvrade, a 8 inch course of averefie
concrete and again the 3 inch course of excellent concrete,
with the Wire mesh between the two courses of concrete. mhe.
steel mesh reinforcement used weiohed 4 noundc nor square
yard. The reason for the two C“UPSeS was said to be that the

vibrating machines in use corld not pronerly vibrate 8 or 9

inches of concrete in one onereticn. The manufacttrers of
those machines claimed that they would do t7e job, and proved
it to the inspectors, whereupon the procedure was modified
again and the whole slah was laid in one course. In 1958

when steel besan to become scarce, tre use of *he reinforcing
mesh was discontinued, and to compensate the slab was

thickened from one to two inches, making a total thickness of

9 to 10 inches. In all cases the slab was of uniform thickness

with no widenins at the edees.

Immediately following the application of the sand
cushion, they constructed parallel to the center line on each
side of the proposed concrete pavement, submerged flat topped
courses, that on the outside are 39 inc es wide and on the

.

inside 15 inches. These courses were left 2 inches below the
surface of the finished pavement and afterwards surfaced with
a bituminous mixture to the level of the concrete. Several
types of forms were used, but one of the most common was the
form with a rail set into the form braces. All eQUipment
traveled on these rails, so that it was possible to have the
subcrade made almost perfect and kept in that condition until
the concrete was poured. These rails were usually 70 pound

steel rails and the sleepers they were set on were about

8 inches thick.

Just previous to nlacins the concrete, waterproofed
paper was laid on the sand cushion. This not only prevented

water heins absorbed from the concrete, but also assists in

-77..

diving the slab freer movement for expansion and contraction
Ave to reduced friction. The use of this heavy paper W98
extremely important especially with the no-slump mix that

was used.

Germ n hiahwgv ennineers apparently were not
content with the macoinerv which we are accustomed to here.
Perhaps in this resnect, more than any other, lies the major
difference. Efiuipment on a concrete pavement was several
times as large as we would see here. Individual machines
weiched as much as 20 tons. Actual construction was carried
out by means of a construction train containing all the
necessary machinery. This ecuipment, spanning the entire
25-foot-wide pavement slab, was carried on the steel rails
which, in turn, were mounted on the concrete shoulder strips
as previouslv mentioned. Some of the machines moved under
their own power. The constr ction train contained 56
constructional units, including wooden huts for construction
engineers, tempers for consolidatine the sand cushions,
machines for spreading the underlav paper, concrete mixers
for base coat, concrete spreaders for the first mixer,
concrete tamper for the first mixer, concrete mixer for the
top coat, concrete tamper and Spreader for the second mixer,
concrete finisher, and tent covers for the finished slabs.
During the operation of laying the pavement slab itself,
the concrete was finished to a special steel form installed

inside and braced ajainst the steel rails. Hand finishing

-'78-

 

V
o .

'T‘fi’fwfi .‘r z. . '
‘ . . . . ‘ ’

“v.
V. I

Figure 1:5
Construction on the Autobahn South of Stuttgart

A. Mixer discharging a batch of concrete into the
spreading hopper. B. Hopper moves forward under
the sunshade and discharges. D. After spreading -
note the very dry concrete. E. Vogele finisher
starting its second pass. F. The final finish
secured after several passes. C. Watering curing
mats over final finish - note light rail which was
used to carry sunshades.

was rarely used. Following the six construction machines
was the superintendent's office, also on wheels, and behind
that a series of large screens constructed on steel frames
mounted on wheels. If caught by rain, these screens were
immediately placed over the freshly laid pavement to protect
the surface. This eliminated the danger ef scalingfiin a
rain without any protection. These screens also protected
the concrete surface as part of the curing, being of heavy
enough material to keep out the heat of the sun. There

were also screens over the top of the finishing machines for

the protection of the Oerators.

An extremely dry mix was used, but with the very
heavy equipment, there was a minimum of finishing required,
and as a result there was very little trouble from scaling.
The surface was required not to snow more than a 5/16 inch
variation; the contractor was required tc grind the surface
(under the watchful eye of a hard-boiled inspector) to
comply with this regulation. Concrete cylinders were taken
from the completed pavement at varying ages on every half-mile
of road for testing purposes. Besides these and tests on all
constituents of the concrete, tests were made on samples from

the mixers.

Batching was effected by weight, usually at a
railway siding which might be several miles from the
construction site. The agcrevates were delivered by rail to

sites from wnich skips were charged with the correct mix.

-80..

The cement was then added and the skips transported to the
mixers on the construction site. The rater ratio varied
from 0.4 to 0.5 depending on the aggreaate, usually with

73 more water in the top ccurse than the lower. An example
of a bottom-course concrete used on the Mannheim-Yarlsruhe

road is quoted as follows:

Water - Cement ratio - 46$
Cement, per cubic meter - 525 Kg.
Cement, per hatch - 500 Kg.

Proportions of mix

500:1800 kg.
Water per batch - 158 liters

The normal cement content of the concrete was 588 lbs. per

cubic yard. ‘Thet portion of pavement which was laid in one

course, near the end of the construction period, was of this

uniform quality throughout. The surface finish of the road

was checked by an irregularity detecting machine, which

gives an autocranhic diagram.

The mixer Was sometimes mounted separately and
sometimes on the same frameas the spreader. Spreaders were
of the vertical-discharge houper type. After receiving a
load of concrete they were discharged by moving the hopper
slowly from one side to the other as the entire machine
moved forward. The extremely dry mixture is entirely unsuited
for use with an ordinary power-driven screed, which exerts
comparatively little compactive effort but merely smooths

‘

the surface after the concrete has been distributed by the

-81-

spreader. German engineers have developed several types of
compaction enuipment. In fact, considerable r search apoears
to have been conducted on the problem, the results of which
are available in a detailed report by R. Schade issued in

1940.

There were two general types of finishers used on
the motor roads, the Vosele and the Dineler. The V0 ele was
a three-element maCfiine, the first and third elements beino
reciprocatine screeds of the usual tyne. Wounted between
the screeds was a heavy plate which could be operated either
as a vibrator or a tamper. Vibrating fre uencies were
oriiinally nuite low (150-050 per minute) but were later

ncreased to as hich as 3,d00 per minute. It was sometimes

Ho

operated alternately as a tamper and as a vibrator in
successive “D°°Pq: ””3 Pre"hen*1y several passes were re uired
to obtain the desired finish. The Dingler machine was a very

ace of equipment. It consisted of a series of

H0

much heavier p
tampine hammers, with 4- by lO-inch faces, weighing 55 to l20
pounds each and mounted in a row just behind the front screed.
The heidht of fall was about 6 inches and they were operated
at about 70 blows per minute. These tampinc hamiers were
apparently only used for compactinQ t*e lower course. The
final finishing was by means of a comhined screed and tamper
operating at about 600 strokes per minute and several passes

were usually reouired to produce the required finish.

Another unique feature was the practice of conducting

- 82 -

 

Figure 14
.' Construction on the Autobahn North
of Kassel using the Dingler machine.

A. Concrete mixer spanning subgrade with industrial
railway on the right. B. Tamping machine in action
compacting the lower course - note dry mixture.

D. The appearance of the concrete in the surface
course before and after compaction by the tamping
screed. E. The finished surface being given a light
brooming. C. The low sunshades used during the
preliminary curing. F. Woven—reed curing mats shown
in place. These were left in place for 3 weeks and
were kept continuously wet during that period.

-83-

the placing, finishing, and preliminary curing operations
under sunshades. These were mounted on light wooden frames
spanning the entire pavement and carried on light steel rails
mounted outside and parallel to the concrete shoulder strips.
In this way the concrete was protected from sun and wind

from the time it was placed until it had hardened sufficiently
to receive the final curing mats. The frames used for
protecting the concrete during placing were sufficiently

high to permit the equipment to pass under them and to
accomodate the men working on the final finish. The frames

used for the preliminary curina were low and were completely

enclosed.

The shelters only covered the fresh concrete until
it had set, usually one day, and then curing mats were placed
over it. The crring was done in different ways. In some

rth

.0

cases very heavy cocoanut matting was followed by damp e.
or sand and allowed to stand for three or four weeks. In
other cases, after the shelters passed forward, the surface
behind them was covered with plaited straw mats, or sand, and
kept wet for three wee s. Sometimes the donorete was watered

every day for about a week after this protection had been

removed.

Construction, in general, was full width in one
operation, with a longitudinal center joint_of the weakened
plane type. But lane-at—a-time construction was occasionally

used, the longitudinal joint between the slabs in this case

being of the butt type. Light steel tie bars were used
across the longitudinal joint to nreve t separation of the

pavement slabs due to settlement or other causes.

The transverse joints are all expansion joints
1/2 inch wide at the bottom and 5/4 inch wide at the top.
The spacini of transverse joints varied widely, however.
The first laid were installed at an irregular spacinq of
50-49-50 feet and no dummy joints were used. This irregular
spacing was to overcome the rhythmic effect of the uniform
joint spacing. These joints had dowels across them. In
most cases the length of the slabs was determined in relation
to road curvature and subsoil conditions, as will be shown

later in some handbook specifications. later construction

showed uniform spacing of joints. For nonreinforced sections

the joint spacing was generally 26 feet, whereas for reinforced

ngs varied from a minimum of 59 feet to a maximum

0
Ho

sections spa

of 98 feet. An average expansion joint spacin from 40 to 60

L7»?

feet. Weakened-plsne contraction joints were frecuently
installed,narticularly in the Case of the longer expansion-
joint spacings. The joints were formed with a wooden batten
about 5 in. deep placed and left at the bottom of the slot.
Above this a Wieland jointing strip, 2}" deep, was laid and
the concrete was then laid continuously without reoard to the
joints, so that there is a thickness of about %" of concrete
at the top of the joint about the flieland strip. This latter

is a hollow steel form, 2 l/B inches deep and 3/4 inch wide.

-85-

It is made in lengths of about 12 feet and before being
placed in position is painted on the sides with bitumen. It
fits over the wooden batten and lies above it, as already
explained. Immediately after the finishint machine had left
the surface of the concrete, a shelter on wheels, running on
rails, with a platform a few inches clear of the concrete was
run into position. Men working in this shelter removed the
concrete on top of the Wieland strip and finished off the
arrises by hand. The Wieland strip was left in the concrete
for three or four weeks, steam then being blown into it
through a hole at one end and passing out through a hole at
the other end. This procedure melted the bitumen and the strip
was then withdrawn. The space, 5 inches deep between the
concrete slabs, above the wonden batten was then filled with

bitumen and asbestos. The wooden batten remained in place.

In a handbook issued in 1957, desc ibing methods of

"S

concrete highway construction on the German motor roads, it is
stated, ”Joints shall be spaced 3% to 50 feet apart. The
lencths of successive slabs need not be varied. In mild
equable climates, on stretches, in flat country or in exca-
vations (if foundation conditions permit), and in cold weather
construction, wide spacing is nermissable, a narrower spacing
being requisite if the annual temperature rarme is considerable.
On high embankments, lower embankments of recent construction,

on subqrades which are unstable or where the ceoloqical

character varies considerably, in hot-weather construction or

-86..

on curves of less than 550 feet radius, the spacing may be
further reduced to a minimum of 20 feet where conditions are
especially unfavorable, such as approsCEes to larce engineering
structures. Cn bridge abutments the joints should be of the
expansion tyne 9nd should not be dowelled. The former

practice of varying the length of road slabs has been abandoned
because (a) the denier of rescnance effects is negligible;

(b) increased stabilitv can now be ensured by use of dowelled
joints. All joints are to be formed at richt angles to the
rcad axis, the possible utility of oblique joints becoming
neélifiible at hish speeds. Joints are to be continued across
the full width of the pavement, since it was found that

stassered joints may cause the formation of cracks,

As re:ards_dowellin2 of joints, dowels shall be
provided in all cases where frost heaving or subsidence is
likely to occur. The dowels must permit lonfitudinal
movement of the slabs and transmit stresses across the joints
without injury to the concrete. They must therefore be placed
accurately in relation to the Gradient and direction of the
pavement, and midway throufh the thickness of the slab.

Round dowel bars in eVpcnsion joints shall he at least 0.8-1

inch in diameter and 2G inches lonf, average spacing is 12

inches, a closer spacing being adapted neon the corners.

Dowels shall be connected by steel flats with
blunted edses or supported by concrete blocks. The round end

of each bar is left evposed, the tapered end being painted

- 87 -

with a thin insulating coatinn of bitumen and protected by
a cap which permits 0.9 inch expansion of the bar, packed
with cork, shavings, etc. The holes in the joint inlays fit

the dowelled bars very accurately.

Transverse dummy joints are dowelled in the same
way as exnansion joints but the bars are 0.7 inch in diameter
and are not canted. 0n curves of less than 2,000 feet radius
and on stretches where subdrsde conditions are known to be
unsatisfactory, anchor bars 5 feet long and 0.56 to 0.54
inch in diameter must be provided across longitudinal or
transverse expansion joints, in the middle third of the slabs,
in order to permit lonéitudinal movement at both ends. The
prescribed spacing in 30 inches. Similar bars should be
provided across the full width of exnansion joints on stretches

where irregular subsidence or frost heaving are likely to

occur; also in longitudinal dummy joints alone the full length

0

of slabs at intervals of 5 feet.

TEmphasis is placed on the necessity of nrovidinc
proper sunport for dowel bars and for completing the whole

joint assembly before it is placed in position."

Germany's hiahway program was much different and
on a very much larger scale than anything that country had
ever attempted before. The construction of new nvtional
motor hichways alone very modern lines and the improvement

of about 25,000 miles of existing roads, meant nany new

-88-

ecuipment recniremnnts. Beca se of economic conditions

very little machinery could be inported, which meant that

they had to develop new equipment and that this be done in

a rather short time. while in some ways their ecuipment
development had followed alonf lines very similar to that

with us here, there are many cases “here, because of certain
different influences, it has been very much different. One

of the thinys which seemed to have had the greatest effect

in general desidn and nethod of operation was hauling ecuip-
ment. Back of this, possibly the lack of petroleum for motor
fuel and rubber for pneumatic tiresmade it necessary for them
to use the industrial railway all the way throudh construction
from the start of excavation to the completion of the slab,
instead of motor operated pneumatic tired, or crawler equip-
ment which is general practice here. Also, Germany did not
have an automotive industry with its mass production, making
available a wide range of alloys and special features of
desifn as we have. These have had a very definite influence
on our construction equipment. This, coupled with the general
tendency of the German engineer to build larqe heavy machinery
for the same type of work was brouaht out by several different
companies at the same time. his naturally made many detailed
differences, which, along with not too nreat a tendency for
standardization, made two machines which were exactly alike
somewhat of an exception. As has been indicated, most of the

hauling all the way through the construction of a hichway was

U

done by the industrial railway. In sore cases, on grade
construction, the cars were loaded by hand, and if the grade
was not too steep, moved by hand, but generally they were
either loaded by power shovels or long conveyors fed by
hand and moved by am 11 locomotives, either steam or diesel.
Fundamentally the power shovel used for excavation in grade
construction was similar to that used here. Steam was the
most common, but with a tendency toward diesel in the newer
models, which were mounted on crawlers, very similar to those
common with us. There were many detailed differences and a
general one of interest is the dipper door attached by two
large arms, one on either side and near the top. To dump
the load the door was swung on an arc across the bottom of
the dipper, sliding from under the load. This saves height
but takes considerable pull through a long distance to dump
the complete load. Another method was to use a system of
gears and a brake drum attached directly to the back side of
the dipper. A spring loaded brake holds the door in closed
position and to dump the load this brake is released, instead
of using the latch as was common practice here. They used
some large shovels, but most of those on highway work were

about one-half cubic yard in size.

While very heavy machinery was used in building
the express f0°fl9’ ”at” ”“8 proceeding also on the old high-
ways of various types. That system comprised 212,000 km.

There was a strong demand for all sorts of mechanical

eduipment. As it was more practical to overpass the narrower
local roads, the eXpress roads run mostly through cuts.

Heavy excavating machinery was employed. Narrow-gage track
paralleled the work. Industrial locomotives and dump cars

were used.

All of this greatly stimulated the highway machinery
industry. The industry had pretentious exhibits at the 1957
spring fair in Leipzig. Diesel engines were used almost
entirely in a wide range of sizes. Pneumatic tires were
employed on a surprisingly large proportion of the equipment.

a.

Tire treads oI artificial rubber were used. While synthetic
rubber costs more than the natural product, its resistance
to abrasion makes its use practical on tires to be put to

particular hard use.

The exhibits showed a strong tendency toward
welding in the manufacture of machinery. Provision for
minimizing oilinq was made by enclosing gears and by use
of anti-friction bearinvs. Portable crushing and screening

4"

plants were made in a multitude oi sizes. Demonstrations

of rock drills and pavement breakers constituted one of the

features of the fair. Wary improvements in th's type of
eruinment were claimed, areatly reducing the need for

blastinfi. Improvement was clfiimed on the vibratory motors.

Vibrators permit the use of coarser actresate.

Tractor track said to have a much lender life than

that previously used was on exhibit. Improvements in trans-
mission permitted greater speed on some of the motorized
equipment. Dirtmoving machinery, small and large, was much
in evidence, as were compressors and pumps in wide variety.
As Germany was particularly proud of its chemical products,
considerable space was devoted to wood preservations and a
variety of tars. Much was claimed for chemicals that

accelerated the setting of concrete.

These scattered additional facts are of interest:
The rate of progress on the Autobahn varied slightly but the
average was about 240 yards of 24 foot 6 inch roadway in an
eight-hour day, and about 440 yards for a double shift. The
record was 580 yards per day. The surface finish obtained on
the work is of the fine grain or sandpaper characteristic.
A coarse aggregate or broom.effect was carefully avoided.
Such grinding as was necessary to bring the level of the
pavement within the required accuracy was done in a number
of places on the Berlin-Brunswick road, but grinding was
almost.unknown on later work. Owing to the severity of the
winter climate the work was carried out for the most part

only in the summer and autumn.months.

About 5 per cent of the roads had bituminous
surfaces. These surfaces were retained for those cases where
resilience of construction.was required, either because of

doubtful properties in the subsoil or where slight crust

- 92 -

mmvements were anticipated. The foundation was of hand-picked
Telford stone with a macadam.subcrust. The total thickness

of these two was about 11 inches. The bituminous-concrete
surface was usually laid in two courses, a base coat of 2 1/2
inches and a surface course of 5/4 inch, giving a total con-

solidated thickness of about 5 1/4 inches.

In concluding this chapter it might be of interest
to give a brief summary of a typical section of highway built
in Germany in the vicinity of Berlin, as part of the so-called

"Berliner-Ring."

The figures quoted cover the construction of
approximately 22 miles of highway constituting only a small
part of the entire "Ring" which circles the city at an

average distance of about 20 to 25 miles from its center.

The excavation, or grading work was started in the
fall of 1954, and finished in the summer of 1956. At two
places it was necessary to dynamite swamps and replace them
with fresh material. At another point it required the
raising of a railwayiB feet in order to pass under it. With
the grading finished in the summer of 1936, the section.was

paved and open to traffic on June 5th, 1957.

In the construction of this highway the following

organization was required:

Five large grading contractors; two contractors

applying the sand cushion, six steel companies erecting
bridges; twelve paving and concrete structure contractors,

and about forty medium and smaller firms.

The average number of men employed during grading

was 1,500 and an additional 800 for the levelling.

For the bridge construction there were about 2,000
men working daily in 5 shifts for several months. It was
noticeable that very rapid progress was made in all bridge
work. Altogether there were about 1.5 million working days
utilized.

Equipment used included the following:. 55 miles
of railway tracks; 1,100 dump cars; 50 locomotives; 15

large shovels and 20 large concrete mixers.

More than 5,000,000 cu. yd. of excavation was

necessary, and 625,000 sq. yd. of concrete pavement.

In this pavement there was 56,000 metric tons of
cement; 180,000 metric tons of gravel and 100,000 tons of

sand.

In the approaches and junctions with the main high-
way there was 95,680 sq. yd. of granite paving blocks used

and 60,000 sq. yd. of gravel and sand.

In the elimination of grade crossings it was
necessary to erect 58 structures as follows: 15 overhead
bridges of which 2 were steel; 2 steel structures over

-94..

railways; ll subways; 4 tunnels; 5 archway crossings; 1 large

bridge crossing another main highway and a double valley.

This structure required 45,000 cu. yd. concrete;
1,452 tons structural steel; 5,750 tons steel for other uses;

and 915 cu. yd. masonry work and 80,000 bricks.

The biggest bridge on the section is the one crossing
the Hudersdoff Valley. In the first viaduct, 2,968 ft. long,
is an embankment 2,400 ft. in length with an average height

of 50 ft., and another viaduct 787 ft. long.

In the construction of the bridges whose piers were
concrete encased with stone masonry, it was necessary in the
case of 5 piers to put them.down 50 ft. below the surface by
means of compressed air caissons. All steel construction was
by electric welding. Additional materials used in.the other
structures were: 7,500 tons of structural steel; 65,400 cu. yd.

of concrete; 520,000 bricks and 410 cu. yd. of natural stone.

CHAPTER VII
CONDITION OF THE AUTOBAHN TODAY

We have covered the entire history of the Autobahn
up to the war, but what of its use during the war and its

condition now? This chapter is devoted to that subject.

-APrior to the war the Autobahn was used to good
advantage by buses and trucks, as well as automobiles.
During the war all forms of transport were completely taken
over by the Reich. Motor fuel was conserved for the armed
forces and little use was made of the Autobahn except by
the troops and supporting industries. As motor fuel became

scarce, motor cars were transformed to wood burners.

Comparatively speaking therefore, the roads were
carrying very little traffic, either prior to the war or
during it. In 1959, rough counts on the road between Berlin
and Brunswick and on the road between Heidelberg and Mannhebm
showed, in each case about 150 vehicles per hour, or roughly
nine vehicles per yard width per hour. The traffic on the
Autobahn observed during the summer of 1947 was very'light
both as to the number of vehicles and the axle loads. Harold
Allen and F. H. Jackson of the Public Roads Administration
made the survey just mentioned and noted that in traveling
during a Sunday afternoon from Helmstedt to the outer Berlin
circle, a distance of 70 miles, no vehicles were seen in a

period of 45 minutes. Six light trucks were counted in the

70 miles. In many places in this area and other sections of
the Autobahn, the pavement had not been discolored by the oil
streak parallel to the center line which usually results

from the passage of a large number of heavy motor vehicles.
The appearance of the pavement indicated that the greatest
volume of traffic on the system.was from Frankfurt to Kassel,
south of Frankfurt toward Heidelberg, and from Frankfurt to
Hannover via the Ruhr Valley. Due to the very light traffic
on the system, now and in the past, it is difficult to make
any comparison of the pavements with.those in the United
States laid under similar climatic conditions and on similar
soils. It is likely that the volume of traffic on most of the
primary roads in the United States is considerably greater

than was observed at any location on the Autobahn.

Since the present condition of the Autobahn is
largely dependent on the climate that exists in Germany, it
is in order to examine that climate here. Western Germany
has a milder climate than would be expected from its latitude
because it is exposed to mild westerly winds. There is little
difference between the north and south sections since in the
latter the higher elevations counterbalance the southern
location. The mean annual temperature of Hamburg is 48°F.,
of Leipzig, 47°F., and of Munchen, 45°F. The average annual
rainfall varies from 16 inches in the plains to 47 inches on
the southeast uplands. July is normally the rainiest month

and January or February, the driest. The snowfall occurs

-97..

during the months of January, February, and March, and in
that period snowfall occurs about 50 days in the northern

lowlands and 50 to 50 days in the southeastern highlands.

It would be difficult to select an area in the
United States having an extensive mileage of concrete pavement
in which the soil and climatic conditions are exactly the same
as those found in Germany. The area including southern
Michigan, Ohio, Indiana, Kentucky, western Pennsylvania, and
West Virginia has similar geologic formations, soil conditions,
‘and a fairly comparable climate. The temperature and rainfall
data for six cities in the selected area of the United States
and for four cities in Germany, as supplied by the United
States Weather Bureau, are shown in the following table:

COMPARISON OF CLIMATOLOGICAL DATA FOR
GERMANY AND MIDWESTERN UNITED STATES

 

 

 

 

 

Temperature
Annual
City Average Variations average
rainfall
Jan. July Max. Min. Range

Germany: °F. °F. °F. °F. °F. Inches
Berlin ............... 50 64 99 -15 114 25
Hamburg _____________ 52 65 92 - 6 98 29
Frankfurt....__._"_ 52 66 100 - 7 107 24
Munchen___-mu_-_-._ 28 64 97 ~14 111 56
Average________-m 50.5 64.2 97 -10.5 107.5 28

United States:
Indianapolis, Ind.- 28 75 107 -22 129 58

Columbus, Ohio_-__- 51 75 106 -20 126 54
Pittsburgh, Pa.___- 52 74 105 -20 125 55
Charleston, W. Va.- 58 77 108 -17 125 46
Frankfort, Ky.___-_ 56 78 111 -17 128 45
Lansing, Mich._._u_ 25 71 102 -26 128 51
Average__"__--___ 51.5 75 106.2 -20.5 126.5 57.8

 

 

 

 

 

 

 

 

* Over a period of 55 to 75 years.

A comparison of these data shows that the average temperatures
for January are approximately the same in both areas, that

the average July temperatures in the United States cities are
approximately 10 degrees higher, and that the range from
maximum to minimum is greater in the United States. The
rainfall in Indianapolis, Columbus, or Pittsburgh is comparable
to that of Munchen, but for the rest of Germany it is lower
than that of the middlewestern area of the United States.

Data as to the penetration offrost in Germany were not avail-

able from the weather records.

The use of the paved shoulder strips, described in
detail previously, has been effective in keeping the traffic
on the pavement. As a result, there has been no rutting or
destruction of the sodded area of the shoulders. The sod is
very thick and tough and even though there has been very little
mowing or other care given to the shoulders or embankment
slopes, they are in good condition and look reasonably neat.
The asphaltic surfaces of the shoulder strips are generally
in good condition. Occasional local failures may be noted.
Typical views of the shoulder strips can be seen on the

pictures in Chapter IV.

fii Reports made as a result of inSpections of the road,
in 1959, within 70 miles of Berlin, made the following remarks:
The concrete constructed in 1954 and 1955 had not cracked as
much as that constructed before 1954. This was attributed to

the fact that machine finishing was laxitroduced in 1934. It

- 99 -

was noted that unreinforced concrete laid on a cambered road
without a longitudinal joint had cracked at the center of
the roadway where the width was 15 ft. or more, and that
unreinforced slabs more than 50 ft. long had some transverse
cracking. Several of the roads which had a considerable

number of cracks carried very little traffic.

All of the structural defects that usually develop
in concrete pavements in the United States are to be found
but, aside from.frequent transverse cracking, defects such as
joint spelling and faulting, settlement, etc., are not serious

except in the Frankfurt area.

Transverse cracking is common and is not confined
to any particular part of the system. There seems to be no
relation between transverse cracking and terrain or soil
conditions. In.most instances the cracks are closed and are
not discernible at speeds normally traveled by automobiles.
In some cases the cracks are open and the expansion joints
have closed. This condition was noted on a section just north
of Gottingen, near Kassel. Transverse cracking seems to be
most pronounced on the route from Hannover to Frankfurt
through the Ruhr Valley, from.Frankfurt to Kassel, and from
Frankfurt toward Heidelberg. The cracking shown in the

figure 15 is typical.

Spelling at transverse and longitudinal joints

was found principally in the area around Frankfurt. At the

- lOO -

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H _-g- -- "-" ’2‘ ' “gm—'3‘"? ~ mu; .

“2:.“ -W--’~—.~- .f' u—. ”‘5“
5- “fl.

. main
. ' , ‘_ v ‘IW

0!

 

Figure 15

Figure 17

A. Faulting in the outside lane
in Ruhr-Frankfurt area. The
photograph was taken with the
camera facing in the direction
of the traffic and it should be
noticed that the expansion
joints in the left lane, which
had not faulted, are visible
while those in the right lane
have had faulted sufficiently
to be obscured. B. Warping
resulted in.high joints on the

. Ruhr-Frankfurt road. C. Surface

scale was seen only on the

Munchen Salzburg route.

 

- 101 -

transverse joints this appeared to be due in.most instances
to the infiltration of sand and other incompressible debris
into the joint and the subsequent overstress of the concrete
upon expansion of the pavement. Figure 16 illustrates the

spelling at joints in the vicinity of Frankfurt.

The following are exerpts from Jackson and Allen's
report: Faulting at joints and at transverse cracks, in
most instances less than 1/4 inch, was observed in areas
where there was evidence of a considerable amount of traffic.
At a location approximately 50 miles west of Kamen faulting
of joints in the outside lanes of the pavement was found to
be 1/2 to 5/4 inch. In the Munchen-Salzburg section there
were a few small corner breaks. With few exceptions, these

were the only corner breaks found.

Some faulting and some spelling were observed at
the longitudinal center joints. In many instances the

longitudinal center joint was crooked.

The riding surface of the pavement over a consider-
able portion of the mileage inspected was poor as compared
with standards in the United States. For example, in the
section from.Berlin to Braunschweig the pavement was rough
and there were many small areas where there was evidence
that bush hammering had been resorted to in an effort to
produce a better riding surface. On the other hand, there

were many long stretches of smooth-riding pavement. Here

- 102 -

.0»- .4wn-n... .-~.~....'
.
.

arrrWTTiia-x We - _ 7mm 35-;

-'4I'

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Figure 16

Spelling at joints occurred principally
in the vicinity of Frankfurt.

- 105 -

again, there appeared to be no relation between the degree

of smoothness and soil conditions, terrain, or other factors.

Evidence of mud pumping at joints in the concrete
pavement is not found on the Autobahn. The absence of pump-
ing over the areas where fine-grain soil subgredes predominate
may be attributed to the passage of relatively few heavy loads
and to the use of a layer of granular material such as sand
or sand-gravel under the pavement. The sealing of the
eXpansion joints and cracks to prevent the entrance of surface

water was inadequate.

Warping was observed in a short section 51 miles
south of Koln. The soil in this area is a silty clay and
would be susceptible to sufficient volume change with an
increase in moisture content from.a dry compact state to
cause warping. The layer of cohesionless granular material
usually used under the pavement on the Autobahn would not be
effective in preventing warping. Observation of this section
was made during a light rainstorm and the water falling on
the pavement was running away from.the joints, indicating
that they were high. This condition is illustrated in figure

17B.

So far as could be determined from an examination
of the surface of the pavements and from chip samples taken
from the corners or edges of the slabs, the quality of the

concrete, with few exceptions, appeared to be excellent. The

- 104 -

concrete had a good ring under the hammer and the difficulty
encountered in breaking off the chip samples revealed, in
general, a high degree of strength and toughness. As a
further check on quality, a number of the chip samples were
examined under the microscope in an effort to determine some-
thing of the character of the matrix, the presence and

nature of voids, etc. Thin-section examinations were also
made of many of the igneous aggregate types found in the
samples. The examination of the chip samples revealed the
concrete generally to be of excellent quality. There was no
evidence of excess water. On the contrary, with the exception
of a sample of bridge concrete, such voids as were noted were
quite large and evidently of air origin, indicating that
mixtures of very dry consistency had been used. This is
borne out by the construction record. The bond between
matrix and aggregate particles was in practically all cases
sufficiently strong to fracture the aggregate particles
themselves, again revealing good strength and probably a

high degree of durability.

In the microscopic examination a magnification
of 20 diameters was used, with a change to 50 diameters when
some special detail seemed to indicate the desirability of
the increased power. In none of the specimens was there
any evidence of water gain beneath the lower surfaces of the

aggregate particles.

A characteristic feature of the pavement surface is

- 105 -

the general absence of the rather heavy mortar top which we
frequently leave on our roads and which so often scales off,
leaving the surface rough and unsightly. An examination of
the surface indicated, in most instances, the use of a mix
that contained just enough paste to fill the voids in the
aggregate and leave a small excess for finishing. Surfaces
were dense and compact, with the coarse aggregate either just
below the t0p or actually exposed in some degree} Typical
illustrations of variations in the surface texture are shown
in figure 18. Figure 18A is a view of a surface on.which
the screed marks are still showing. The corrugations are
quite shallow and are about 1 inch apart. This particular
photograph was taken just east of the Bad Oeynhausen inter-
change on the road to Hannover. Other sections showed the
same condition, particularly on the inner lanes which, of
course, carry less traffic. Note in the lower right illustra-
tion that coarse aggregate up to 1 inch in size,‘which is
close to maximum size used in the tOp course, is exposed.
Many of the exposed aggregate surfaces are smooth, with a
terrezzolike texture, probably the result of slight surface
wear. In many places this type of surface was noted in.the
center of the traffic lanes (particularly the outside lane)
with the original thin mortar surface showing at the extreme
edges. In other sections where the coarse aggregate was
exposed, particles of the hard igneous rock protruded slightly
above the mortar, producing a slightly rough surface. This

condition may have resulted from the scaling off of the light

- 106 -

 

Figure 18

A. In some places screed marks still appear as
shallow corrugations. B. A fine-grained sand
finish. C. Black colored concrete. D-F.
Typical appearance of varying degrees of coarse
aggregate exposure.

- 107 -

surface mortar or it may have been.the result of wear -- it
is difficult to determine the exact cause. However, it
should be emphasized that the slightly rough surface is not
objectionable from.the standpoint of riding quality. Neither
should the exposure of the aggregate have any detrimental
effect on the ultimate durability of the concrete, since the

quality of both aggregate and concrete was excellent.

There was evidence of surface grinding in several
places. This was undertaken, evidently, to correct irregu-
larities resulting from.the difficulty of finishing the very

dry concrete generally used.

With the exception of one section in southern
Germany, the entire 1,000 miles of pavement covered by this
inspection were found to be practically free from scale,
either of the surface or of the progressive type. Only on
certain stretches of the Munchen-Salzburg section in Bavaria
was surface scaling noted in any appreciable amount. Figure
170 is a general view of the pavement showing about the worst
condition observed. This picture was taken about 20 miles
west of the Austrian border at Salzburg. Figures 19A and C
are details showing the type of scaling that has developed '
on this section. It is apparently of the surface type only;
that is, the concrete below the scaled areas appeared to be
sound. Figures 19A and C indicate a rather heavy layer of
surface mortar at this point and this fact, coupled with the

possibility that the winters in this region, due to its high

- 108 -

elevation, may be somewhat more severe than elsewhere in
western Germany, may account for the scaling. However, in
this connection it should be noted that, according to

weather records as shown previously, the average January
temperature at Munchen was only slightly lower and the annual
rainfall only slightly higher than for the more northern

cities.

It has been stated that the scaling which deve10ped
on the Munchen-Salzburg section at a relatively early period
was due to the use of inferior aggregate. A chip sample
taken at the approximate location shown in figure 19A did not,
however, reveal the presence of an appreciable amount of
inferior material, although the petrographer did indicate
that the coarse aggregate in this sample was an "altered
granite." Just how much the generally poor subgrade conditions
in this area, or other factors, may have contributed to the

scaling is not known.

Only isolated scaled areas, all of the surface
type, were noted elsewhere on the system. Figure 19D is a
detail of a local scaled area on the Frankfurt-Stuttgart
section, a few miles shuth of Frankfurt. From.the standpoint
of general condition this is one of the poorest sections on
the Autobahn. As previously noted, considerable spelling at
joints has also developed on this section. Figure 198 is a
detail showing a thin surface scale on the Hannover-Ruhr

section, about 50 miles east of the Bad Oeynhausen interchange.

- 109 -

  

 

  

.. w "fl.p .."‘-"a. .J'_.
‘ i .' . I ." . ‘ . . d,
, n {’d .0 V ‘t u!—.-” if"! “$.- ~ W0 ‘ .
-VWW,A..'WHM;L;V~T " “ ' “ fl ' I 1‘ ” ‘ '

_.,‘-.' ..

Figure 19

A-D. Surface scale occurred commonly on the
Munchen-Salzburg route but only isolated cases
elsewhere. E,F. Incipient disintegration,
revealed by D lines, was found only at one
place on the systems

- 110 -

 

This pavement, as well as many other portions of the system,
had evidently been sprayed with bituminous material at some
time, probably for camouflage purposes. The scale here is

not deep enough to affect the riding quality of the surface.

Incipient disintegration of the concrete, as
revealed by the formation of so-called D lines along the
edges of the pavement and along joints, was found at only
one place on the system; a point on the Munchen-Salzburg
section where the worst scaling was found. The D lines in
this case were found along the outside (north) lane and
were very fine. The condition is shown in figures E and F.
In the United States, cracks of this type have come to be
associated with the beginning of disintegration due to

accelerated weathering.

The general freedom of the motor roads from scaling
and other troubles associated with severe weathering may be
attributed to the following factors, the listing not necessar-
ily being in order of importance:

1. The general excellent quality of the aggregates.

2. The low water-cement ratio (usually 0.45 or less,
by weight).

5. The practice of designing mixtures and compacting
concrete in such a manner as to avoid the formp
ation of a heavy surface layer of mortar.

4. The comparatively mild winters.

5. The fact that chloride salts were not used for

- 111 -

ice removal.

6. Thorough curing.

The possible influence of all of these factors is
fairly obvious. The role of the cement is not so apparent.
According to Swayze's report, mentioned in Chapter V, the
cements used in the Autobahn were distinctly inferior to
those manufactured in this country. However, the concrete
is good and from this fact we can conclude at least that it
is possible to make good concrete with the German.cements
provided the other conditions are right. Whether these
cements would perform any better than the American cements
under conditions that prevail in the Northern part of the

United States is another matter. .An intensive research

program.would be necessary to answer this question.

5? The Autobahn.was damaged little during the war
aside from its bridge structures. The Germans demonstrated
stupidity in destroying the fine bridges of the network in
their retreat. Whereas destruction of one span would have
rendered a bridge completely useless to the Allies, the
Germans demolished the entire structure in most cases. The
roads themselves were not damaged to any extent; however,
railway lines were almost completely destroyed. 'Reconstruction
of these bridges has been in progress since shortly after the
end of the war. Some have been completed but others are
still in the process. Transportation as a whole was ruined
and decades will probably elapse before it equals the once

efficient system which existed.
- 112 -

CHAPTER VIII
CONCLUSIONS AND RECOMMENDATIONS

As mentioned in the body of this report, the com-
paratively light traffic on the German motor roads, particu-
larly as regards the movement of heavily loaded vehicles,
as well as the comparatively mild climate, make comparisons
with the performance of concrete pavements in this country
difficult. This is especially true if we attempt to compare
the Germany primary roads with the heavy-duty concrete pave-
ments of the industrial States of the north and middle west.
Many of these roads undoubtedly carry a far heavier volume
of truck traffic than any of the motor roads in Germany.

The question therefore is: How would the German roads perform
under similar climatic and traffic conditions? It is, of
course, impossible to say definitely. However, these two
factors -- the low volume of heavy truck traffic and the
relatively mild climate -- probably account for the compare-
tive freedom of the German motor roads from structural
defects and that, under comparable climatic and traffic
conditions, the structural performance of the German roads
would be about the same as the average concrete pavement in
this country. This opinion is borne out by the fact that
structural failures such as joint spelling, faulting, etc.,
were found to be more numerous and, in general, more serious
on sections of the system where the indications pointed to

the heaviest traffic.

- 115 -

We must also recognize the beneficial effect of
using a layer of granular material under the pavement,
particularly with respect to the control of mud pumping at
joints, a condition which was not found anywhere on the

system.

The quality of the German concrete was excellent.
Although the design strengths were not unusually high as
compared to standards in use in the United States, the
indications were that a high degree of uniformity was
obtained. This may possibly be due to the care used in pro-
portioning mixes, as, for example, the use of several sizes
of aggregate and the practice of limiting the maximum size
in the top course to about 1 inch. Reference was also made
to the general absence of the relatively heavy mortar tOp
which we see so often on our roads, and to the fact that
this might have reduced the tendency to scale. It is
believed that the principle of consolidating the pavement
slab by vibration is good although the Germans may have gone
too far in their effort to use excessively dry concrete.
This is indicated by the rather rough surface with occasionally
noted evidence of grinding off of high Spots. However, the
principle of using as dry a mix and as low-sanded a mix as
can be consolidated properly by the effective use of vibratory

equipment is good and should be encouraged in this country.

The uniformly excellent durability of the concrete

is probably also due, in part at least, to the excellent

- 114 -

quality of the aggregates generally used. This is also a
factor to which we might give more consideration in the United

States.

The probable influence of long continued and
thorough curing alsoshould not be ignored. Whether the
elaborate precautions for protecting the fresh concrete
from.sun or wind were always necessary is problematical.
However, the practice of thorough water curing, although
old-fashioned in terms of modern American practice, is still,

in the opinion of the author, the preferred method.

Regardless of the quality of the cement used, the
quality of the concrete was excellent; concrete containing
Eisenportland (portland-blast-furnace slag cement) was, on
the average, as good as concrete containing straight portland
cement. Although it was impossible to determine on just
what portions of the Autobahn the Eisenportland was used,
it was stated to have been used on about one-third of the
total mileage. This fact would seem.to warrant the statement

that its performance was satisfactory.

As a result of a study of methods and practices
employed during the construction of the Autobahn and also
of its present conditions, the author recommends that steps
be taken to initiate a comprehensive program of research
on each of the following subjects:

1. Study of the possibility of insuring greater

- 115 -

uniformity in pavement concrete by reducing the maximum
size of the coarse aggregate.

2. Deve10pment of more effective methods of com-
pacting concrete in pavements by mechanical means, such as
vibration, tamping, etc.

3. Study of the effects of variations in the
chemical composition of cements and the methods of manufactur-

ing cements on the properties of concrete.

With the initiation and completion of these studies,
perhaps the super highways, which this country will continue
to build in the future, will be free of many or all of the

defects so common to concrete pavements now.

- 116 -

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Monthly Labor Report .
Bu-SineSS Week 0 o o o
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Engineering News-Record
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PUblic VJOTKS o o o o 0
Canadian Engineer .

Roads and Streets . .
Engineering 0 o o o 0
Engineering News-Record
The Engineer 0 o e o o o

The Engineer . . . . .
Compressed Air Magazine
Economist . . . . . .

Railway Age 0 o o o o o
The Canadian Engineer .
The Canadian Engineer .
The Canadian Engineer .
American Concrete Instit
Engineering 0 o o e e 0

Public Works

Society of Automotive Enginees

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ed-eeeooeoeeeeeeeeeoee

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o o o 0 June,
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1955
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1957
1957
1958
1958
1958
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1940
1946
1948

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