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THE CONTROL OF VEHICULAR TRAFFIC

AT
STREET AND HIGHWAY INTERSECTIONS

WIS FOR THE DEGREE 0F c. E.
Warren Edward De Young
1931

 

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' IE COITROL 0P VEHICULAR TRAFFIC
A!
STREET AND HIGHWAY IRTERSECTIOHS

Thai: for Degree or 0.3.
wARREN EDWARD puns
1931

GHAPTERI

CHAPTER'II

mm In

CHAPTER IV

CHAPTER?

CHAPTER 71

CHAPTERVII

GHAPTER VIII

CHAPTERIX

TABLE OF CONTENTS

Statement of Problem

Control by City Ordinenoel and
State Lon

control by Polioe end. civic
Organintione

Direction of Traffic Without
Control Signal!

Signal Control or Truffle

Vehicle Ac tultOd Control

The Science of Signal Location
Superhighway: and Elevated Highnye

An Outlook into the Future

121873

Page

11

81

37

58

6‘7

PREFACE

It is impossible to acknowledge all the
sources from which I have received help in propor-
ing this paper. In the past few years it has been
my privilege to discuss treffio with the leading
authorities in the North Central and North Eastern
United States. I have also found it necessary to
discuss traffic in a business ray vith many hundreds
of persons in the Middle Western States who are mak-
ing vehicle traffic studies an interesting vocation.
These interviews have given me many sidelights on
the traffic situation as it now exists and certain
definite views on how the situation can be relieved
from its present turmoil.

Professor 0. L. Allen, Head of the Civil
Engineering Department at Miohigan State college
receives my thanks for making this thesis possible.

The following have discussed many of the
ideas expressed in this paper and have not disegreed
too violently: Professor Morrison of the University
of Michigan: Professors Jenda, Van Hagen and Owen of
the University of Wisconsin; Professors Wiley and
Crandell of the University of Illinois; Hr. George
Brown of the Michigan State Highway Department;

Ir. J. H. Miller of the Illinois Division of High-
nys; Mr. William Haenig of the Wisconsin State High-

say Department; Mr. '1'. T. Wiley of the University of
Illinois, Mr. Oscar Gunderson of the Traffic Division
of Flint, Michigan; Captain Ray Sprague of the Traffic
Division of Grand Rapids, Michigan; Superintendent Potts
of theirsffio‘Division of Detroit, Michigan.

I wish to thank the following for valuable data
they so kindly supplied: nr. Reeder and an. Baker of the
National Safety Council, Mr. Simpson of the Institute of
Traffic Engineers, and practically everyone on the Traf-
fic Staff of my own organization, the Automatic Signal
Corporation.

CHAPTER I
STATEMENT OF PROBLEM

Within the last twenty-five years the traffic pro-
blom has risen from a position of relative unimportance in
civic and national affairs until it has booms a major pro-
blem. There are several reasons for this: within the last
twenty-five years the automobile has become a vehicle of
everyday transportation to the multitide and industry has
made increasing use of trucks in moving raw materials and
distributing finished products. Within the same span of
years the United States has changed from an essentially
agricultural nation to one of the dominant industrial
countries of the world. This change has caused a great
increase in the pepulation of the cities. Thousands of
people live in a very small area. Host of them leave
their homes for work at approximately the same time and
thousands of them leave their work at the end of the day
to return home at approximately the same time. Thousands
attend sports events, theatresor, merely drive for
pleasure, wish to arrive and depart at the same time. The
streets have often been found inadequate to carry the flow.

In his address before the Institute orrmrrie
Engineers, Mr. John P. Hallihan gives some interesting
figures which I will quote:

”Fifty years ago, in 1880, the papulation in
cities constituted but 28.6 per cent of the total of the

nation. Today the urban population has risen to 56.2
per cent, or the percentage has practically doubled.

I'T-uentymfive years ago, in 1905, there were
only 78,000 motor vehicles in the United States operating
on 160,000 miles of improved roads, or one to every two
miles of road.

'At the beginning of 1930 there were 26,500,000
motor vehicles operating on 663,000 miles of improved roads,
or 40 vehicles per mile of road. 3,400,000, or 12.75 per
cent are devoted to commercial use of which 92,500 are
motor buses used for public transportation. The remainder,
23,100,000, or 87 per cent are private automobiles used for
private or individual transportation - enough, with a little
crowding on the front seat, to carry all the people in the
nation.'

These conditions have combined to create a very
serious problem. The problem was a slight one at first,
but very quickly it became obvious that highway and street
intersections were points of traffic congestion and traffic
accidents. Officer control was the first step, but as the
number of intersections requiring control increased multi-
plying the numbor of men required, complete officer control
became economically impossible.

Some sort of protection was required, however,
and the adoption of the railroad type of signal light to
govern the movement of vehicles followed. The use of an

alternating type of flashing mechanism such as was used

3.

for advertising signs, while it was admittedly the simplest.
solution of the problem of when and how to change the indi-
cations of these signals, was obviously not a solution.
This indicated the necessity for the application of an
amount of engineering analysis and ingenuity proportional
to the importance of the problem.
However, the situation was allowed to drift on
in this rather makeshift fashion until the toll exacted
by traffic congestion and accidents had become alarming
and was increasing at a rate even more alarming.
Eventually the engineers of the country began
to seriously consider these matters and indeed they met
continue to do so to an increasing extent before the pro-
blem will be solved. The results of their efforts are
already beginning to be apparent, and we are beginning
to realise that the traffic problem cannot be solved by
hit ormiss methods but can and will be solved only by
fundamentally sound economic and engineering analyses.
Definition of Terms. The definition of terms is
from the Hodel Municipal Traffic Ordinances published by
the Rational Conference on Street and Highway Safety.
Street or Highway. "Every way set apart for public travel,
except foot paths. The term street or highway is defined
in as few words as possible and to embrace every street
area in its entirety, including sidewalks. Requirements
of law in some states may necessitate a further elaboration

with specific reference to particular types of public ways,

4.

such as bridges, viaducts, vehicular tunnels, boulevards,
avenues and other descriptive terms. However, in most
states such enumeration is unnecessary, as all the various
types of roads are held to be covered by the phrase 'Every
way set apart for public travel.‘

Intersection. The area embraced within the prolongation
of the lateral curb lines or, if none, then the lateral
boundary lines of two or more streets or highways which
Join one another at an angle whether or not one such
street or highway crosses the other.

Vehicle. Every device in, upon, or by which any person
or preperty is or may be transported or drawn upon a
public highway, excepting devices moved by human power

or used exclusively upon stationary rails or tracks, K
i’raff c. Pedestrians, ridden or herded animals, vehicles,
street cars and other conveyances either singly or together
while using any street for purposes of travel.

Effical Traffic 51%;. All signals, not inconsistent
with this Ordinance, placed or erected by authority of a
public body or official having Jurisdiction, for the pur-
pose of guiding, directing, warning or regulating traffic.
foicial Traffic; 35911:. All signals, not inconsistent
with this Ordinance, placed or erected by authority of a
public body or official having Jurisdiction, forthe pur-
pose of directing, warning or regulating traffic.

_i[raffi_g Control M. Any device using colored lights,
or suds, or any combination thereof, whether manually,

5.

electrically or'mechanically operated, by which traffic is
alternately directed to step and to-proceed.

m Officer. Every officer of the Municipal Police
Department or any officer authorised to direct or regu-
late traffic or to make arrests for violations of traffic
regulations.” ‘ H

Lack of Uniformitl'in Present gonsideration of
Subject. There is not only a lack of uniformity in the
type of control to be used under similar traffic condi-
tions, but, also, a lack of uniformity in the govern-
mental agencies which have control of the problem.

We find almost every conceivable governmental
bureau and department in control of certain phases of
the traffic problem. It is Jugglcd back and forth among
police departments, superintendents of streets, park boards,
safety departments and the like. It has been found that
when one department has been made responsible and given
control of the problem much more effective work has been
mowlished than when the work was divided among many
ms and no definite plan of control ever worked out.
In State and Gmmty governments, the work is usually much
better done, chiefly because the problem is considered by
technically trained men.

It is sometimes true that department heads will
rule adversely on the reconraendations of members of their
staff who have studied the problem fully and thus nullify
excellent plans. Politics often play entirely too immort-

6.

eat a part in this problem. Pullic economy is often sacri-
ficed at the expense of political expediency.

The lack of uniformity in the methods of traffic
control has been one of the contributing factors to the
seriousness of the problem. This has been the subject
discussed by national committees and groups of traffic
engineers. Dr. Miller hcclintock in his articles in the
'Ameriean City" for September 1930, states: "With forty-
eight states and many hundreds of cities empowered to con-
trol traffic, it was inevitable that the early stages of
traffic regulation should show an utter confusion in con-
trel rules and methods. To some extent this confusion
still exists, but the progress which has been made to-
ward uniformity in essential rules of Operation is scarce-
ly short of remarkable.“

The Reeg of Impressing Municigal Authorities
filth the Serious Aspects of the Problem. Two character-
istics of this country's traffic problem that should be
emphasised even more than its magnitude are its increasing
rate of growth and the insidious nature of its growth. The
striking figures measuring its present importance are
certainly such as to be viewed with alarm, but when it is
realised that these figures will be increased next year by
increments much greater than those which constituted last
year’s increase, it will be obvious that there is even
greater cause for concern. It is not enough that preventa-

tive measures be drawn up to take care of the present rate

7.

of increase and also to reduce the present total losses,
but traffic relief plans should be made which take into
consideration that soon just the increase may exceed what
is new the total.

coupled with. this continually increasing rate of
grosth is the equally alarming way the problem is growing
without attracting the attention of the general public.

In reading or hearing of losses of life, property, or
valuable time, the public is impressed only by the case
in hand, and, rarely stops to consider its effect on acci-
dent frequency or severity rates. Briefly then, the pub-
lic who would be the first to clamor for protection and
relief if it fully understood to what a serious degree it
was being taxed by traffic, does not in any sense appre-
ciate either the magnitude of the problem or its ever“
increasing and treacherous yowth.

The facts and figures by shich this tribute to
traffic can be measured should be divided into three groups-e
the tribute in lives lost per year, property damage due to
accidents, and value of time lost through traffic congestion.
If sense major catastrophe should occur or epidemic sweep the
country resulting in 31,500 deaths people would be appalled
at such a tremendous loss and it would be the principal topic
of conversation for a long time. Yet, who, if anyone, gets
terribly excited by the fact that 31,500 human beings lost
their lives in motor vehicle accidents last year? This
means that 86 lives are sacrificed per day. This toll of

8.

lives is increasing greatly each year. What is even more

» important than the total number of deaths is the rapidly
increasing death rate per unit of population. From 18
:deaths per 100,000 population in 1926, the rate has Jumped
to 23 per 100,000 in 1930. This not because of the increase
in number of cars, for the death rate per 100,000 registered
automobiles has risen from 95 in 1925 to 107 in 1930. All
this has occurred even though great strideetoward a higher
degree of safety have been made by autOmobile manufacturers
in the line of more and better brakes, easier steering
facilities, greater car stability and so on. In the short
space of ten years, motor vehicle deaths have increased
300%, that total is growing each year. It is appalling

to consider the year 1940. Even the sacrifice of 31,500
lives demands very strenuous effortsfor better traffic
regulation and the knowledge of the growing danger leaves
no excuse for delayed action.

The recent stock market collapse caused a save of
depression to sweep the entire country and necessitated
imediste action bythe government for the restoration of
business confidence. It has been conservatively estimated
that the actual money loss resulting from motor vehicle
accidents in the same year as the stock market collapse,
has exceeded $1,000,000,000, and yet this caused as ex-
citement. The loss per person amounts to $10.00. When
figures such as this are offered to the public, the reac-
tin of the individual is likely to be, "I haven't any car

9.

so it doesn't cost me anything," or "I was insured so my
accident wasn't any loss to me.‘I moss individuals are
actually paying large ammts in spite of their insurance
or freedom from accidents. Insurance companies pay for a
post number of accidents, but the individuals pay the
compmies in insurance prcnfimns. Insurance rates have
increased during the last few years and increases are
called for by greater losses. Even if the individual has
no automobile, he is paying insurance premiwxs for the cars
that serve him, delivery can, taxis", buses and so on. All
losses are not inclined in the estimated totals, for many
accidents amount to so little that no record is kept of
them and the total of these exact be tremendous. Further,
about 1,000,000 peeple were injured in 19230 and navy of
the bills for medical service never get to the staticians'
record files, nor do losses to their ermloyers in lost time
and decreased production.

The Hon. Robert P. Lamont, Secretary of Ccmaeree
of the United States stated in a report to the Third
Rational Conference on Street and Highway Safety, {1930)
that it was estimated that an annual loss to American
business of more than $2,000,000,” was due to traffic
congestion. This could wt to $30.00 per parsm in the
United States. The same facts hold in regard to this less
as did for the losses due to accidents. to all must pay
elu‘ share. Even if the individual does not pay with his
can time and gasoline, the losses are passed on to him by

10.

others. If it were not for congestion, the trucking or
delivery capacities of the companies serving the individual
would be greater with fewer cars. The individual must pay
for the extra care and drivers in his bills for service.
These losses are not the totals of what other people are
paying, but quietly and surely they creep into every
individual's bills in one form or another. How much
better it would be to tax people directly for far smaller
amounts than present losses, for the double purpose of
cutting down the present sacrifice and retarding the future
govt}: of the tribute to traffic.

The yearly tribute in the form of traffic lo sees
and in accidents and congestion has already seamed un-
believesble proportions and gives definite promise of
increasing by larger mounts each year. The present rate
of pregress of the country in adapting better methods of
traffic regulation is lower than the rate of increase of
the severity of the control problem.

geasons ‘for Limiting Studluto Control of Moving
VQMQ08_.$ digest intersections. The traffic problem is
W of many closely related parts. It is scarcely
possible to consider one phase of the problem without deal-
ing with other phases but it sould be impossible in a paper
of this length to deal thoroughly with the entire problem.
For this reason this study will be limited to the control
of moving vehicles at street and highway intersections.

11.

CHAPTER II
CONTROL BY CITY ORDINANCES AND STATE LAWS

In 1927 Mr. Hoover, then Secretary of Commerce
appointed s. committee to draw up a Model Municipal Traffic
Ordinance. An analysis or the traffic ordinances or one
hundred American cities together with the model ordinances
existing in several states and a study was made of the
subject matter appropriate for an ordinance adaptable to
the needs of mieipalities throughout the country. This
material was published in the form of a model ordinance.
It is recommended for the consideration of all commities
contemplating revision of their traffic ordinances and
desiring to see nation-side uniformity in traffic regula-
tions to the greatest degree compatible with local require-
ments. I will quote from this model Ordinances

Ordinances governing right of my.

s. ”The operator or s vehicle approaching an
intersection shall yieldthe right of say to a vehicle
thioh has entered the intersection. When two vehicles
enter the intersection at the same time, the operator of
the vehicle on the leftshall yield the right or way to
the vehicle on the right.

I). 'The Operator of s vehicle within an inter-
section intending to turn to the left across the path of
any vehicle approaching from the cppc site direction may
make such left turn only after giving a signal as required

12.

by law, and after affording a reasonable Opportunity to the
operator of such other vehicle to avoid a collision.
Ordinances governing speed.

a. ”Any person driving a vehicle on a highway
shall drive the same at a careful and prudent speed not
greater than is reasonable and proper, having due regard
to the traffic, surface and width of the highway and of
any other conditions than existing, and no person shall
drive any vehicle upon a highway at such a speed as to
endanger the life, limb or preperty of any person.

13. “Subject to the provisions of subdivision
(a) of this section and except in those instances where s
loser speed is specified in this Ordinance, it shall be
prime fscie lawful for the driver of a vehicle to drive the
same at s speed not exceeding the following, but in any
case men such speed would be unsafe it shall not be lawful.

1. "Fifteen miles an hour when approaching within
fifty feet of a grade crossing of any steam, electric, or
street railway when the driver's view is obstructed. A
driver's view shall be deemed to be obstructed when at any
time during the last two hundred feet of his approach to
such crossing he does not have a clear and uninterrupted
view of such intersection and of the traffic upon such
railway for a distance of four hundred feet in each direc-
tion from such crossing;

3. "Fifteen miles an hour when approaching within
fifty feet and in traversing an intersection of highways

13.

when the driver's view is obstructed. A driver's view
shall be deemed to be obstructed when at any time during
the last fifty feet of his approach to such intersection,
he does not have a clear and uninterrupted view of such
intersection and of the traffic upon all of the highways
entering such intersection for a distance of two hundred
feet from such int erseot ion:

6. I"l'wenty miles an hour on any highway in a business
district, as defined herein, when traffic on such highway
is controlled at intersections by traffic officers or step-
andegc signals; .

8. "Thirty-five miles an hour under all other condi-
tions. It shall be prima facie unlawful for any person to
wood any of the foregoing speed limitations. In every
charge of violation of this section the complaint, also
the summons or notice to appear, shall specify, the speed
at which the defendant is alleged to have driven, also the
speed which this section declares shall be prima facie law-
ful at the time and place of such alleged violation."

' Ordinances Governing Parking Where
Capacity of Intersections Would be Affected.
Sec. 25. Model Municipal Traffic Ordinance.
”Stepping Prohibited in Specified Places. It shall be
unlawful for the operator of a vehicle to step, stand or
park such vehicle in any of the following places, except
when necessary to avoid conflict with other traffic or in
compliance with the directions of a police officer or

l4.

traffic control sign or signal:

l. ”Within an intersection.

8. ”On a crosswalk.

3. “Between a safety sons and the adjacent curb or
within thirty (:50) feet of points on the curb immediately
opposite the ends of a safety sons, unless the traffic
usthority mall indicate a different length by signs.
lots: It is rscomsnded that in no event should vehicles
he stepped or parked within fifteen (15) feet of the end
of a safety zone. The exact distance to be specified might
depend upon the width of the roadway, volume of traffic
and other material factors. '

4. ”Within twenty-five (25) feet from the intersection
of curb lines, or, if none, than within fifteen (15) feet
of the intersection of preperty lines at an intersection
except at alleys. I

3. 'Within thirty (30} feet upon the approach to any
flashing beacon, stop sign or traffic control signal located
at the side of the roadway."

Ordinances Governing the Class of
Vehicles Which May Use an Intersection.

"Truck traffic has become a factor of such
imartance that proposals 'for its regulation are being
made in several sections of the country,»-

‘Regulation must, of course, take account of the

comercial and industrial need for truck transportation

15.

and therefore should make proper provision for deliveries
withindistricts and on streets where trucks otherwise are
prohibited”. Quoted from M. H. T. 0.

“Millions of dollars in losses are being con-
stantly experienced by labor, capital and the owners of
valuable business sites thru delays experienced in the
traffic maelstrom of every large city. nevertheless, we
permit the individual, regardless of the nature of his
errand, the almost unrestricted privilege of driving an
old dilapidated hulk into the very heart of a congested
business district and then storing it in public street
space worth thousands of dollars while he goes about his
private business - if he has any. I say ”almost unre-
stricted" privilege because we are beginning to impose
some regulations with reapcct to where and how long he may
leave his conveyance. We are also beginning to give some
attention to the mechanical conditionof the vehicle and
the qualifications of the driver. But, considering the
seriousness of present traffic congestion and current
accident rates, we have barely started to exercise the
degree of control which the situation demnds. lior have we
even recognised yet, in addition to the factors above, the
need for giving attention likewise to the nature of the
errand which brings a driver into a congested area.

"The suggestion has been seriously advanced that
all private vehicles except under special permit, be pro-
hibited from entering very heavily congested central city

16.

areas. An alternative suggestion has been that of requir-
ing the use of a distinctive municipal tag with a nominal
surcharge for all private vehicles desiring to enter and
park within congested areas. In the determination of
measures for the improvement of traffic conditions the
needs of the conmmnity as a whole must take precedence
over the imediate interests of any particular group or
section. Only upon the principle of the greatest good to
the greatest number may so achieve that substantial improve-
ment in conditions on our streets and highways which is so
badly needed.” The above paragraphs were quoted from
Charles Gordon, Managing Director or the American Electric
Railm Association, New York City.

Education or Motorists ageiELOrdinances. The
effectiveness of the work or the police force and signals
depends more or less upon the traffic habits of drivers
and pedestrians. The National Safety Council advises that
educational activities be undertaken in seeperation with
local safety councils, chamber of Commerce, automobile clubs
and other civic organizations. They make the following
suggestions:

"This can be done through continual publicity in
newspapers, by speeches, thru the schools and by means of
traffic law enforcement, brake and headlight campaigns,
poster publicity and similar methods;

1. "Impress motor vehicle drivers and pedestrians with
the seriousness of traffic accidents through publication of

17.

of statistics. most peeple sill make a greater effort to
avoid accidents if they are made to realize their serious-

ness.

2. "Eli-.rphasize particularly that wandering minds, need-
less haste and lack of courtesy are the chief causes of
street accidents.

3. "Law enforcement is good educational work, since
it makes an example of the law breakers.

4. “Advocate better training for automobile drivers.

5. “Abstracts of traffic laws in easily understandable
form should be prepared and distributed to the public.
Avoid in this matter all technicalities and legal terminol-
ogy which who so many booklets on traffic laws and regula-
tions hard to understand.‘

"If possible, have a member of the police depart-u
ment spend part or all of his time in public educational
work. Let him see that every person who uses the streets
knows as much about traffic as possible. If he is diligent
and does his work intelligently, he will reduce the troubles
of the remainder of the traffic force and should be many
times more valuable than he would be on ordinary police
duty.'

. Enforcement of CitLOrdinances as Affecting
Intersectionsl Control. ”Without careful, fair and firm
enforcement of traffic regulations by the police, there is
little hepe of securing safety for either pedestrians or

vehicles. Safety education based upon adequate legislation

18.

must be backed up by the police force. Police action be-
comes especially necessary at intersections where there are
large numbers of turning movements, for these movements
interfere with pedestrians proceeding on the ”go" signal.
Officers can do much to regularise these turns and to
restrain over-anxious motorists from endangering the safety
of pedestrians. There is a mistaken ides quite prevalent
that police officers standing by and doing nothing to help
turning vehicles or to protect pedestrians. The signals
should be regarded as a means of relieving. the officer
from mechanical routine, so that he may use his intelli-
gence to keep traffic moving with greater safety." Says
Ralph Robinson, of the San Francisco Traffic Survey
Carmittee.

Many methods and expedients for improving and
remedying the enforcement situation were pointed out in
the report of the Committees on Enforcement and on Causes
of Accidents of the Hoover Conference in 1926. I will
quote from their report:

”more are three broad methods of approach;

let, through prevention and safeguard,

2nd , through much stronger punishment for violation
of the rights of others,

51, through public education as to its responsibil-
ites.

"Special traffic courts are recommended for the

largest cities, and special traffic sessions of the general

_ ...—4m. “."- .- I l‘

19.

courts for smaller cities. Uniformity will be promoted if
the traffic cases are handled by the smallest nwnber of
Judges able to handle them. Judges who confine their
attention solely to traffic matters are most likely to
administer adequate and evenchanded Justice.

"Successful law enforcement is impossible in the
long run without the backing of. public Opinion. The
organization of public Opinion to support law enforcement
must be Just as continuous and Just as energetic as the
efforts to defeat it. The aim should be to create a
comnnty feeling that the traffic police and courts are
performing an important public duty.II

Control by State have.

In an attempt to secure uniformity and more
efficient methods of control and to curtail unwise expendi-
tures of local governments several states have passed laws
giving the state Jurisdiction over traffic regulation.
Massachusetts, Rhode Island, Connecticut, and New Jersey
have such laws. Michigan and Illinois have laws which
grant some power to the state government in traffic matters ._
Wisconsin has such a bill pending in the state legislatm-s.
State Jurisdiction seems to be gaining headway. From an
economical standpotnt there is much to be said in favor of
centralized control. Federal Jurisdiction in traffic
regulation has even been advocated, it is improbable that
such control will ever materialize due to many obstacles

a
£4 ‘

and constitutional difficulties that would arise.

In new Jersey a legislative act was passed in
1950 which provides for the mointnmnt of e. traffic
comzissien of four members with "power to regulate and
control the placing and Operation of all traffic signals
an signal devices upon the streets, highxmys and public
places in the state, or cause the removal of traffic

sigmls determined to be mmccoeeary".

 

 

21.

CHAPTER III
CONTROL BY POLICE AND CIVIC ORGANIZATIONS

From a survey of 103 cities ranging in population
tion from 20,000 to over 218,000 the National Safety
Council found the size of the traffic police force, in
preportion to population to be quite uniform. in average
city of 100,000 population would have a normal traffic
police force of 31 men, 25 on traffic duty full-time and
the remainder serving part-otime. Cities of all sizes show
a miform average of from three to four traffic officers
for each 10,000 people. This furnishes a measure which
may be applied to any city. If the traffic force has only
one-half or two-thirds as many, it is under-manned. Or,
if the force already comprises four or more men for each
10,000 of pepulation and the handling of traffic is un-
satisfactory, the trouble probably lies in impreper or
inefficient management, peer training, lack of or impro-
perly located signals, ordinances which are difficult to
enforce, or lack of cosperation with the courts, which

causes excessive court attendance of traffic officers.

Traffic Divisions of Police Departments.
Coincidental with the growth of traffic is the
demand for specialised traffic activities of the police
department. Starting probably with a single officer
assigned to full-time traffic duties, traffic divisions

. ---fi§‘ ~71; ‘- ‘

..‘na‘. (I.

22.

have been established in all cities of over 500,000 p0p~
ulation and in about 100 smaller cities.

The Traffic Division is usually authorized by
the City Council, or other legislative body; however the
Chief of Police or Public Safety Comnissioner can establish
it as a part of his administrative duties. It is important
and should be himy specialized. To obtain uniformity of
administration it should have complete control of the traf-
fic in the entire city and should supervise all police

officers while on traffic duty.
To be effective in reducing accidents as well as

congestion, the National Safety Council recommends the
following for a traffic division:
'1. A competent, responsible head.

2. A specially trained personnel.

3. A proper point of view with regard to its public
responsibility which is to promote safe, efficient, and
pleasant use of the streets. With this goes a recognition
that the traffic division is dealing with all of the people,
most of whom are willing to do the right thing.

h Jurisdiction over all parts of the city and ewes-
all traffic men, full-time or part-time.

"Without the fourth of these items the success
of the traffic division can be only partial. Without the
first three, real success is impossible.

"Head of the Division. The head of the Traffic
Division must be directly responsible to the Chief of

25.

Police and at least the equal in rank of any other officer
under the Chief. The importance of traffic work absolutely
demands this.

”The head of the Traffic Division should have a
title which indicates the importance of his position.
Sergeant, Lieutenant and especially Captain are the titles
commonly used. The term Deputy Chief is very fitting as
it indicates his relation to the Chief and makes clear that
he is ranked higher than precinct captains over whom he
should have Jurisdiction in traffic matters.

”The duties of the Traffic Division include,
direction of traffic, enforcamnt of traffic laws, investi-
gation of accidents, preparation of accident reports, and
educational activities.

I".t'ha most important part of the traffic personnel
is a capable head. If he has the vision to see the re-
quirements of traffic work, the initiative to organize and
train the men, and the courage to enter activities which
are not ordinarily associated with police work he should
be able to lead a traffic division of which the city may
be proud and for which it may be thankful.

”The part-time men from the regular force should
be under the traffic division while on traffic duty, and
regularly assigned under a full-time traffic sergeant who

should supervise a definite area.”

24.

Official Traffic Commission.

The National Conference on Street and Highway
Safety says:

”It is recommended that every municipality faced
with serious traffic problems should create an official
traffic body made up of public officials. Membership on such
body, would, for example, include a member of the city
legislative body, a Judge of the traffic court, representa-
tives from the street, police, and legal departments, and
also a representative from the park department if it has
any Jurisdiction in traffic matters. Such a traffic body
should advice the city council and the administrative de-
partment of the mmicipality as to the best methods for
administering street traffic regulations and as to improve-
ments and changes requisite for the reduction of accidents
and congestion. The city traffic engineer should be a
member of any city traffic body established as above
suggested."

Unofficial Traffic Committee.

A citizen's traffic comittee, unofficial in
character, has been found advantageous in many cities for
exchanging ideas on traffic matters and harmonizing traffic
officials with the general public. In an address before
the National Safety Council, Dr. McClintock says:

'I want to issue a warning to any public official
who has in mind the formation of a supporting traffic

 

\ 9.0. .eeu .

u. ‘rh‘fi ..

 

LAil.

25.

committee or commission. Don't get a lot of benign,
retired capitalists as members of a traffic committee if
you are forming one. Get rather the hard-boiled operating
heads of the business concerns in the city who are vitally
affected by traffic changes. Get twenty or twenty-five of
them, ready to fight with one another or the rest of the
world if necessary at the slightest opportunity. Throw
into. that group of men some factual information that is
sound and properly analysed, with conclusions that are
clear, and with the implications upon business obvious,
and you are going to get Just as hard fighting support for
an intelligent program of traffic relief as you would get
hard fighting opposition if your program were not preper.'

Sergeant Demaroff, Director of Safety Division
of the Police Department of Flint, Michigan, says: . ”The
key man to the organization is the secretary. Get the
right follow on that Job and you will have a successful
ecmittee. If you ask business men to devote more time
than they feel they can spare from their business, you are
not going to make a success of it.” . .

Burton Marsh, Traffic Engineer of Philadelphia
says: "We have six subccmittees: one on accidents, one
on education, one on engineering, one on legislation and
enforesuent, one on street use (which includes parking,
loading, and all of these uses of the street which right
now are taking so much of the attention of these engaged

26.

in traffic work), and one on off-street terminal facilities,
which is'perhaps a complementary committee to the one deal~
ing with improvement of efficiency of street use, althougl
it has other important functions.”

Junior Safety Patrols.

Nearly every police department has to furnish
protection to children going and coming from school. This
is a very real problem in many cities. School intersection
work is nearly always part-time work for regular patrolman,
but there are places where this requires as many man-hours
as all the rest of the traffic work.

School boy patrols have been effective in the
reduction of accidents as has been proved by a comparison
of statistics in many cities where the patrols have operated
ever a number of years. Some of these cities where they
have operated are Chicago, Cleveland, Detroit, Cincinnati,
Washington and Philadelphia. They are usually formed
under the Safety Division and with the cooperation of the
schools and the automobile clubs .

The the national organization and the local
affiliated motor clubs have been encouraging and directing
this’aafety work for ten years there was no uniformity in
its Operation. In 1930 the A.A.A., the National Safety
Council, the National Congress of Parents and Teachers and
the National Education Association participated in a con-
firms, the ultimate object of which was to produce a

 

standard set of rules and regulations for the Operation of
school boy patrols. A code was adepted by the A.A.A. and
the National Safety Council, to serve as official guide to
all organisations sponsoring school boy patrols. The
following is a pledge which is used in some cities:

”I hereby promise that I will will the duties
of my office as laid down by the Captain of patrols and
in such manner as to avoid accidental injury to myself or
others.

"I furthermore promise that I will at no time
attempt to operate from a position in the roadway or assume
any authority over automobile traffic which, I understand,
., is a function of the City Police Department and the
responsibility of the driver.

'In the interest of Safety, I will cooperate
with my parents, the principle of my school, the «ruler
Safety Council, city authorities and the general public.‘

Many benefits have been derived from these patrols;
children have been educated in crossing streets with care
and at the cross walks. The school patrols have brought
about a better understanding between the police officer
and the school child. There is rivalry between schools in
trying to have the best accident record and it is excellent
training in character and responsibility for the boys.

 

CHAPTER Iv
DIRECTION or TRAFFIC armour CONTROL SIGNALS

Officer Control of Traffic.

At intersections handled by a traffic officer,
there are three ways in which his comands can be trans-
mitted to the drivers of approaching vehicles:

1. He may operate a system of signals lights.
a, He may operate a hand semaphore.
3. He may give signals by means of his hands and arms.

If his commands are given to the motorist by
means of a hand semaphore, there is a distinct tendency
for the officer to become nothing more or less than a
human machine. The efficiency of the officer is decreased
since he is not readily available to straighten out traffic
tangles and to regulate the movements of pedestrians.

If he gives signals by means of his hands, a
great deal of uncertainty on the part of the drivers as
to what his signals mean causes traffic to move slowly.
His hand signals tend to be directed to the individual
motorist rather than to groups of motorists, thereby caus-
ing traffic to move more slowly through the intersection
than would be the case if signal lights were used.

The advantages of having a traffic officer stand-
ing in the center of the intersection consist chiefly in
the fact that his presence acts as a deterrent to speeding
and imprcper driving.

«IO-m7 -n

 

29.

Through Street Control.

Through Streets are useful, their successful
application, however, depends upon an understanding of
chat they can and carmot be expected to do.‘ The apparent
simplicity and cheapness of throng: streets has caused '
them to be substituted for automatic signals there traffic

 

”lads makes actual control of traffic needed, and to be
extended shore no traffic regulation is necessary. I '11!
give twelve conclusions reached by the National Safety
Council in regard to through’s-‘treets.

1. When preperly established, a through street will
reduce collisions between autmobilcs, but pedestrian
accidents often increase, and the net result is ordinarily
no material reduction in the number of persons killed and
injured on the through street.

2. Through Streets relieve adjacent parallel streets
of traffic and cause a reduction of accidents on them; hence
if accidents do not actually increase on a through street,
its establishment is beneficial.

3. A system of through streets can be successfully
used to shunt nonestop crosstosm traffic around the busi-
ness district to avoid ummecessary downtown congestion.

4. Traffic on through streets can more more rapidly
than that on unprotected streets without being granted
special right-of-say privileges. After making a full
step, a vehicle on the cross street should be authorised

Iliiil .3

 

 

to enter under the usual right-ofnnay rules.

5. Through Streets should be selected on the basis
of facts gathered for the purpose. It is irrrportant to
have data on accidents at specific intersections, sources
of traffic, traffic concentration points, locations to be
avoided, amount of non-stop through traffic, and physical
conditions of roadways under consideration.

6. Too many through streets defeat their own purpose.
Requiring the driving public to step too often tends to
belittle the importance of through-street stops, and
makes their enforcement difficult, if not impossible.

'7. Through streets should form asimple interconnect-
ing system'which will be convenient to use and easy to
understand. The most desirable plan is usually a vehicular
loop about the business district with radiating feeders
which lead through residential sections and connect with
inter—city highways but do not penetrate the business
district.

8. A through street should not be established merely!
to include one or I tee dangerous intersections. Let these
be isolated stop intersections. At such places it is -
necessary to require stops on only one ofthe two inter-
secting streets, and sometime from only one direction.

9. Automatic signals are almost indispensable at the
intersections of two through streets and are desirable at
other important intersections along them. Where throng:

streets are continued into business districts as signalized
thoroughfares, the signals should be connected into a
flexible progressive system.

10. To secure the advantages of nation-wide uniformity,
legislation.establishing through streets should follow
closely the "Uniform.vehicle Code" of the National Conference
on Street and Highway Safety and the "Model Municipal
Traffic Ordinance“. Signs should conform.to the recommenda-
tions of the American Engineering Council and the Joint
Board.on Interstate Highways.

11. Public education.regarding the location, purpose,
and. requirements of through streets should be coupled with
continuous firm.enforcemcnt of the step provisions to pre-
vent the through streets from becoming a menace rather
than a benefit.

12. Because motor traffic is continually changing,
through.streets should‘be carefully watched after they are
established to detect increases in accident rate, lack of
effectiveness in re-routing traffic, end.loss of usefulness.

“If successful through streets necessitate this
amount of thought, equipment and labor, they cease to be
the cheap means of traffic control which.has already
enticed.too many cities into their promiscuous adoption."

The through street method of control often works
an.unnecessary hardship on the side street traffic, since,

if the through street traffic is continuous, the side

 

llv VIII.“ ltllllllll s

street traffic does not get an Opportunity tocross the
intersection after it has come to a full step. In many
cases the long periods of delay which are inflicted on the
cross street traffic tend to make the drivers impatient
and they take chances in trying to take advantage of small
breaks in the through street traffic, thus causing danger
to themselves as well as to the through street traffic.

In many cases, the driver on the side street is legally
empowered to enter the intersection under the normal legal
right-ofuway rules. In other words, he is legally per-
mitted to take the right of way from traffic approaching
on his left but is required to yield the right of way to
traffic on his right if it has already entered the inter-
section.

Traffic on the main thoroughfare will seldom
yield the right of way to traffic on a side street regard-
less of the legal principles involved. The driver on the
side street, even though he knows that he has the legal
right of way, also realized that his heirs are likely to
collect damages if he tries to exercise his rights.

The successful Operation of the through street
plan of control depends upon the complete observance of
its stepping regulations. This necessitates the provision
of “step” signs which must be illuminated at night.
Authorities have frequently pointed out that too much
dependence cannot be placed upon signs which depend upon

 

 

55.

headlights of approaching vehicles for their illumination.
It is usually necessary to provide constant police super-
vision of the entire thoroughfare 'in order to prevent
motorists from disregarding "Step” signs which they con-
sider unnecessary. Both of these requirements entail
considerable expense to the city. Drivers on the through
street have a right to expect that no one will cross in
front of them from a side ltreet without warning, and
serious accidents are likely to result from lack of proper
"stop” signs or lack of proper enforcement of the stepping
regulation.

In many cases, pedestrian accidents increase on
a through street over the accident rate for the same street
before it was made a through way. In many cases it is
necessary to provide bridges or tunnels in order to profit
pedestrians to cross the artery without undue danger.

. Traffic signal control provides far greater
opportunity for pedestrians to cross the treat in safety
than the through street method of control and thus furnishes
mch greater protection to both vehicles md pedestrians.

Rotary Traffic Systems.

Rotary traffic is a form of control which, in
nest cases, has been adopted because all other types of
traffic control were impracticable uhen applied to a
complex intersection. If traffic is to be given a definite
'Go' or "Stop" indication, the interfering traffic flows

must be divided into a sufficient number of phases so that
no two flows which are permitted simultaneously can inter-
fere with each other seriously. With complex intersections,
the master of such phases is usually so large that a fixed
time system of traffic light would cause intolerable delay
and congestion because the right-:of-way must be divided
into three or four separate intervals. The proportion of
time allotted to each of these phases must correspond to
the average amount of traffic entering from that phase.
Sines average conditions do not exist more than a few
minutes each day, the timing is necessarily wrong during
all the rest of the period of operation.

The rotary traffic principle sometimes-seems to
offer the best solution to complex problems since all
traffic is permitted to enter the intersection simultaneously.
By forcing all traffic to take a round-about path through
the intersection, the speed is kept low, and the efficiency
of the intersection is probably higher than if a fixed time
system of traffic lights were used to give the right-of-way
to three or four combinations of traffic flows independently.

Theoretically, there are no crossing flows in a
rotary traffic system. In practice it is often found that
very serious crossing movements are introduced, especially
if the traffic is at all heavy. These crossing flows are
nearly always at angles other than 90 degrees and conges-
tion is very likely to result.

 

 

At intersections shore trolley oars pass through
the neutral area around which traffic rotates or around
the natural area in the opposite direction to that pre-
scribed for other traffic flows, serious difficulties are
introduced by the interference caused by these fixed wheel
vehicles.

The neutral area must be large in order to avoid
interlocking of streams of traffic, and, condeguently, the
area of the intersection must be large to provide satis--
factory operation of this system. The providing a neutral
area in the center of the intersection greatly decreases
the amount of street space available-for moving traffic.
It is often necessary to convert to non-productive public
use part of the private property imsediately adjacent to
the intersection in order to provide sufficient space for
traffic to move.

In a rotary traffic system, danger is reduced
by forcing all traffic to move at such a slov speed that.
there is little or no possibility of serious collisions.
In a great many cases the inefficiency of the system is
not apparent except after a careful study of conditions.
All traffic moves nearly all the time, it is true, but the
low speed of movement, due to the interference with other
traffic movements, causes the intersection to become eon-
gested at a very lee traffic density. . ’

With rotary traffic systems, pedestrians are

 

. .3‘ I»D.'\..Iul .

 

...-«.1.

 

 

given absolutely no protection, since all traffic moves
at all times and pedestrians must watch traffic from
several different directions in order to keep from being
struck. It is frequently necessary to keep police officers
at the intersection in order to assist pedestrians across
the streets.

The cost of a rotary traffic method of control
is seldom small shen it is preperly applied. It usually
involves expensive physical changes, in moving trolley
tracks, widening the approaches, and increasing the inter.
sectional area to acconssodate a large neutral some which
if of little or no use for the movement of traffic. If the
rotary traffic area is not properly laid out, the direct
first cost may be low, but its commity as a shale pays
increasing amounts each year as a tribute to the ineffi-
ciency of the system.

37.

CHAPTER '7
SIGNAL CONTROL OF TRAFFIC

Advantages of Electric Signals.

The control of traffic by electric signals
offers several important advantages over any other method
of control. A positive, definite, continuous, easily
understood eomand is aven to all traffic approaching
the intersection at all times.

It provides a definite indication as to
vhether the approaching motorist should stop or go. When
the motorist is given a 'Go' signal the opposing traffic
flows are stepped for his benefit and he can move rapidly
through the intersection without interference from any
other source, while sith rotary traffic he must enter a
me of slevly moving traffic and work his way through it.

Signal control gives an affirmative signal as
vell as a negative signal. With a through street system,
the motorist is given a negative signal but practically
nothing is done to provide him a passage through the
intersection. He is at the mercy of the arterial traffic.

The eletric signal has a higher visibility
factor than the signal of an officer directing traffic.
it a corner controlled by a traffic officer, the motorist
hesitates to use his own Judgment to any extent, conse-
quently the officer mat do all the thinking for all the
traffic on all the approaches. .With sigmal control, each

 

‘ -.~ -.~.

 

 

 

motorist is permitted to use his own judgment to a suffic-
ient degree, so his courtesy and judgement assist him
through the intersection in the most efficient marmer
possible.‘

Traffic signal control offers a great advantage
over any other form of traffic handling'in that it is
possible to co-ordinate the movement of traffic through
an eras or along a through street. With my other form
of control, it is very difficult, or even impossible to
assign the right of say at a series of intersections so
that traffic is permitted to move for a considerable
distance without stepping.

The principal methods of co-ordinating a number
of intersections for traffic control are as follows:
synchronized control, reversed synchronized system and

the progressive wave system.

Synchronised Control.

mu: this system .11 of the interlocked signal
installations give the same cemand at the same time in
a given direction. This system is desigzed to permit
traffic to move a comparatively long distance along the
streets before being stopped. this obviously shows an
advantage over a system which requires the stopping of
vehicles at successive intersections. Since all signals
on a given street show green at the same time, there is
great tendency for drivers to speed so that they may pass

59.

as many intersections as possible before being stepped.
{he accident hazard is naturally increased, pedestrians
being those who suffer the most. With this synchronised
system, it is necessary to use a fairly long cycle in
order that traffic may move a considerable distance before
being stepped. Thus, it is necessary to make the side
street traffic vait for an unreasonable time for the right

If my.

Reversed Synchronized System.

With this system lights are shown alternately
men and red at successive blocks; or the lights at
two intersections may show green shile lights at the next
two intersections show red and vice versa; or the groups
may be made up of three or even more lights eadh. The
green and red periods are necessarily of the same length
except in very special cases, and must be approximately
equal to the time required for a car to travel one block,
two blocks or three blocks, or whatever the grouping of
the signals requires.

In general, an equal 'Go' period for main street
traffic and cross street traffic is not the most desirable
apportioning for any corner, since the traffic is usually
heavier on one street than the other. Hence, by the
adoption of this system, a very important limitation is
imadiately set up in the efficiency which is attainable.
Iith the use of this system preferential consideration is

4:0.

ususlly given to e system having signal colors alternating
st each successive intereection, which usually permits s
short cycle to be used. This short cycle encourages
obedience to the siwls by both pedestrians and motorists
so they ere not forced to suit too long, end also serves
es s sstety rector in providing s definite speed control
for the motorist on the main street. With this system,
however, traffic must be rsther light on the artery, es
the low efficiency of the system, due to the necessity of
giving the srtery end the cross street equal periods of
time st esch intersection, causes the system to become

congested at s was density. much lower than other co-

crdincted systems could handle sstisi‘actorily.

Progressive ste System.

A perfectly designed wave system of trsi'fic
control has an analogy in the phenomenon of standing waves
at up in s cord by vibrating one end of it with s simple
hut-manic motion, the other end of the ewd being fixed. -
It the frequency or vibrstics is sdjnstsd properly, the
card can be msde to essum s sine we." term. the distance
between the moving end end the fixed end of the card then
correspmds to the length of the artery. If the cross
streets intersect the srtery st points corresponding to the
node! of the vibe-sting cord, the enslog is complete for s
theoretically perfect wave system. The ssve traveling from
the source of vibrstion towsrds the fixed end corresponds

41.

to one fleet of cars along the artery and the reflected
was new the fixed end moving towards the source of vibra-
tion corresponds to the fleet of cars moving in the opposite
direction along the artery. The two waves in the cord pass
each other at the nodes with opposite amplitude, thus
cancelling each other so that the cord does not move at
this point. In the corresponding wave movement along the
artery, the two fleets of care, when moving in each direc-
tion, pass each other at the point at which one of the
cross streets intersects the artery. Thus, traffic in
both directions uses the artery during the “Go" periods on
the artery at this point, leaving the balance of the time
available in one cycle for the areas street traffic to

We
It will readily be seen that if the intersecting

streets do not meet the artery at certain predetermined
points, the wave system cannot work properly, If, for
instance, one of the intersecting streets entered the
artery at a point vhioh corresponded to a loop of the
vibrating cord, one fleet of cars along the artery would
pass this intersection without any traffic moving in the
opposite direction, and as soon as this fleet of cars had
passed through, the opposite fleet would arrive there,
thereby making it necessary to keep the right of way on
artery continuously, leaving no time for the cross street
traffic. If the intersecting street enters the artery at
a point corresponding to one between the loop and the node

42.

of the vibrating cord, a small amount of timcmay be left
for the cross street traffic, but the artery must still
take more than its share of the total cycle. It is always
necessary to use a cycle of uniform length at each inter-
section, although varying proportions ofthe total cycle
may be given to the artery and the cross street at each
We

While it is possible to set up a theoretically
perfect wave system, in actual practice it is nearly al-
ways found that the cumulative effect of the multitude of
minor interruptions and interferences to which traffic
is subjected causes the wave movement to have an efficiency
mach lower than that expected. Interferences caused by
cars» leaving parking spaces, cars turning left W
Opposing traffic, trolleys starting and stopping at each
corner, and pedestrian movements across the artery make
it practically impossible for traffic to maintain a pre-
determined average speed. It is necessary to regulate the
wave system so that the most heavily traveled cross street
is given sufficient time to permit its traffic to cross the
misery. It is frequently necessary to restrict the arterial
movement unnecessarily because of the fact that one or tic
cross streets carry very heavy traffic during certain hours
of the day, and unless the timing of the shale system is
changed during the day, it must Operate at a low efficiency
throughout most of the day in order to be ready to tales

care of the heavy cross flows when they occur.

43.

In any fixed time system, the traffic signals
are arbitrarily set in a predetermined pattern and traffic
is forced to conform to this pattern if it is to be passed
through the series of intersections without stopping.
Such a system has no flexibility in the true sense of the
m. After it is once set for a theoretical coordinated
movement of traffic, the traffic mist conform to this
setting or the continuous movement ,is not obtained.

Cementing on the progenive system, Rowland
Bibbine says, ”On a long run of heavy traffic street, the
flexible progessive is nor the only one even moderately
efficient vith a high sips]. capacity. These must be
centrally controlled to very cycle (and speed) according
to traffic and weather conditions, and each intersection
must be timed by itself so as to produce continuous non-
stop progressive movement at a predetermined speed and
with least wastage of valuable street time for light cross
movements. To install less efficient types under such
conditions inevitably imposes an economic burden upon the
community uhichmay become disastrous to public transporta-
tion and disrupt established business and land values Ihich
require stability above all things for continued development."

 

 

.lll..!..|l [lull-I I 11 ..- ...III ‘I: .II

44.

CHAPTER VI
VEHICLE ACTUATED CONTROL.

Any control in which the presence or approach
of a vehicle initiates a cycle may be called a vehicle
actuated control. If the cycle which is initiated by the
vehicle is a fired one, that type of control hat only a
very limited application. The more the cycle can be
modified by the arrival of additional care on the Itreet
which has the right of way or on the opposing street, the
more efficient the control become. If the control is
cognisant of the actual traffic conditions on all
Approaches to the intersection at all times, and if the
control is capable of assigning the proper value to each
- factor VMich its detectors transmit to it, then that
control is worthy of the nan» of full vehicle actuated.

thdamentally, a full vehicle actuated control
assigns the right of way according to the actual traffic
conditions on all approaches to the intersection, acting
on information received from its detectors, which are
located in all approaches. A semiuvehicle actuated con-
trol assign the right 'of way in accordmce with the actual
traffic conditions on one street and the expected traffic
conditions on the other street. In a goat many cases,
the expected traffic conditions on the street in which no
detectors are placed can be forecast with sufficient
accuracy so that the efficiency which is attainable with

45.

this type of control is almost as great as that obtainabl
with full vehicle actuated control. In an installation of
this kind the detectors would be placed on the cross street
approaches to a through street or an arterial highway. In
this case the additional cost of full vehicle actuated
control over semi-vehicle actuated control would not be
economically Justified.

Contrary to general opinion, the vehicle detector
itself is not the most important part of a vehicle actuated
control system. The presence of vehicles may be detected
in any one of a number of different ways. Some methods are
more practicable than others, however, the detection of
vehicles is only the first step towards a real control.
The important question in vehicle actuated control is what
to do with the impulse after the detector passes it to the
control mechanism; and also, how much information the
detector can transmit to the control.

The control should be capable of e xtending the
men period sufficiently to pu-mit each successive car
arriving on the street which has the right of way to pass
mletely through the intersection. In order that the
right of way may be released to the other street at the
earliest possible moment, the detector should be capable

of using this information in giving the car exactly

enough time to clear the intersection.
The simplest possible method of extending the

W period for additional cars would be to give a pre-

46.

determined period for the first car and a single arbitrary
extension of time for additional cars, regardless of their
speed or number. A control as simple as this would be
seriously limited.in its ability to intelligently assign
the.right of say. Only a control capable of receiving
separate impulses from.each.car approaching the intersection,
and capable of acting intelligently on the information.thus
collected.ean attain a'high efficiency.

The control must be capable of remembering each
car until it has had sufficient time to passthrough the
intersection. If ears arrive at the intersection.shile
traffic on the opposing street is using the right of way,
they must be remembered by the control so that they can be
given the right of way at the earliest possible mommnt.

If cars cross the detector and then lose the green light
because of the expiration of the maximum period, the right
of way should be returned to them at the first opportunity,
that is, as soon as cars on the opposing street have
cleared.the intersection.

When the right of way is given to a group of
cars which.have been waiting, it requires more time for
them to get under way and through the intersection than
if they had.not started.from.a standstill. In order to
take care of this, additional time is given.te traffic
under these conditions. The initial increment, so called,
is variable ever a wide range in order to take care of any

conceivable condition on either phase.

4'7.

If the control is set so that each moving car
approaching the intersection is given a protection period
long enough to allow it to pass through the intersection,
and no provision is made for giving an initial increment
for starting traffic from a standstill, it will be found
that two or three cars waiting between the detector and
the stop line will not be given sufficient time to move
through the intersection unless additional ears cross the
detector and extend the green light period. If the pro-
tection period is made long enough to permit standing
traffic to start and pass through the intersection (still
aesmling that the control does not give an initial increa-
Inent), it will be found that the protection period is too
long for efficiency, since stragglers can hold the right
of say. i'he provision of the initial increment permits
the protection period to be adjusted so that the right of
way is used efficiently, while still giving standing
traffic sufficient time to get started.

The control should be capable of stopping a
continuous stream of traffic for the benefit of vehicles
which have been waiting for a reasonable time fer‘an oppor-
tunity to use the intersection on the other phase. It
should also be capable of preventing the right of way from
being held too long on one phase, even thong: no traffic
has called the right of way to the other phase. This .
provides cppcrunity for pedestrians to cross the street
in safety at all times.

48.

The violation of the amber signal has been a
cause of much legislation and discussion. With pretimed
traffic control, the amber period is essential in order
to give moving traffic on Opportunity to stepbefore the
right of way is given to the opposing streets. With vehi-v
ole actuated control, however, full knowledge of the actual
traffic conditions on all approaches is an inherent feature.
The control seldom takes the right of way from moving
traffic, this being done only in case opposing traffic on
the intersecting streets has been saiting for a full
maximum period for an opportunity to use the intersection.
In view of the full information of the actual traffic eon-
ditione vhich the control has, it is advisable and perfectly
safe to show a verylshort mber to the street shioh is
losing the right of way in the event that a gap has appeared
in the moving traffic. If sufficient space has appeared in
the line of moving traffic to permit the right of say to be
changed to the other phase, there is , no one close enough to
the intersection so that any good would be done by showing
a long amber period. Under these eenditiens, the control
should shov only a second or so of amber and then revert
immediately to the ether street in order that the intersec-
tion may be used at its highest efficiency. If, on the
other hand, the control is required to stop a continuous
stream of traffic, an amber period somewhat longer than _
normal should be shown in order to give this traffic
fiftieient time to stop. The discriminating amber, as

 

Ill II‘III I“ llll‘l‘lil

49.

this is called, can be inserted in the cycle by merely
thrcting a switch, and the limits of variability can be
set by means of a dial when full vehicle actuated control
is need.

Full vehicle actuated control ehould be capable
of receiving instruction as to what street to favor. It
can be easily adjusted so that in the absence of traffic
it will alvays return the right of way to one particular
street, or it may be adjusted so that the right of way
always remains on the street which used it last until
needed by traffic on the other street. Semi-vehiele
actuated control is also capable of receiving instructions,
but these instructions are built into the device as an
inherent part of it. This eontrel always returne the right
of way to the main artery, as the heaviest traffic is
expected there.

Vehicle actuated controls are made in mltiphaae
and supermaltiphase typee, as tall as the more common tve
phase type which assigns the right of way to either one of
two streets or combinations of traffic flows. The multi-
phase control can assign the right of way to any one of
four different combinations of traffic flovs or four
different streets. It never shows a green light on any
street on which there is no traffic. It makes possible
the advantages of traffic signal control at intersections
shich heretofore have been too complicated to consider for
signal handling. Supermultiphaee control can aasigi the

right of way to six different nhaces. It can be adjusted
to permit the continuous movement of traffic floss which
do not interfere appreciably with other traffic movements,
stopping these floss only when the intersection is to be
used by traffic flows which would interfere with them.
Both multiphase and supermultiphase controls contain all
the features of vehicle actuated control as described
above, as well as many additional features shich are
peculiar to the needs of complicated intersections.

Installations of vehicle actuated control have
been made in some of the most comlex intersections in
the East, including Park Circle, Baltimore, and Exchange
Place in Providence. Vehicle actuated controls on a
principal thoroughfare may be co-ordinatcd so that con-
tinuous movement of traffic, sithout delay, may be
”tablished.

In his address before the National Safety Council
(1930) Maxwell Halsey, Traffic Engineer for the State of
nassachusetts says: “There are many intersections, parti-
cularly in rural areas, which do not have sufficient
traffic to warrant or permit efficient fixed cycle Operation,
and yet shore high speed or other conditions have resulted
in many accidents and make some sort of positive control
necessary. The vehicle actuated signal, by its ability to
automatically adjust its operation to existing traffic con-
ditions is an excellent safety device even under light
traffic conditions.

51.

”The actuated signal is being timed by the flow
of traffic as it arrives and thus will automatically adjust
its operations to different conditions. This feature is
particularly valuable at rural intersections where fluctu-
ations in volume and proportions are frequent. .

”The detectors or treadles offer a safety feature
where high speeds exist. For example, it is possible to
place the pavement unit back from the intersection equal
to the braking distance for the speeds usually encountered.
If a high speed vehicle hits the treadle upon the green,
he is guaranteed that it will remain goon until after he
has passed through the intersection.

”The Comonwealth of Massachusetts has installed
several actuated signals upon state higlways.‘ One of these
has been in action for more than a year, and the rest for
periods of from 3 to 5 months. The one which has been in
for 13 months has reduced accidents from an average of two
a month, to an average of one a month, a reduction of 50%.
At the other intersections the total of the accidents has

been reduced as well as the severity of each accident."

Oomarison of Delay Caused by Each Type of Signal.
Quoting again from Mr. Halsey's report to the
National Safety Council: ”In order to determine the rela-
tive merits of the different types of control signals, the
State of Massachusetts has started a series of delay
studies. The following statistics give a rough idea of

52.

what may be learned by this method.

'At intersection A, the flow was about 25,000
vehicles from '7 Adi. to 11 PM. on Smday, and 14,000
vehicles on a week day during the same hours. The actual
flow during the study ranged about 500 to '700 vehicles per
hour. The preportion of traffic was fairly equal. The
delay obtained was the actual time lost by vehicles stand-
ing still while waiting for the signal to turn goon. The
losses due to deceleration and acceleration were not
included since they were scammed to be equal for each type
of control. The full vehicle actuated control, with
detectors upon each entering road, showed a delay per car
of 6.84 seconds. The semi-actuated control, with detectors
only upon the minor street, indicated a delay per car of
8.52 seconds. The fixed cycle showed a delay per car of
9.60 seconds. Upon the basis of this delay, the full-
actuated signal gave 29% less delay than the fixed cycle
signal, and the semi-actuated signal 13% less delay than
the fixed cycle signal. The semi-actuated signal did not
shoe up so well at this particular intersection because it
is primarily desigied to control intersections where cross
traffic is much less than the main flow.

“At intersection B, with less traffic and a
greater proportion upon the main street, the delays were
as follows. Full actuated control 2.76 seconds per car,
semi—actuated control 5.42 seconds per car, and fixed time
cycle control 8.40 seconds per car. This showed the full

53.

actuated signal to be 67% more efficient and.the semi-
sctuated control 59% more efficient than the fixed cycle

control."

54.

CHAPTER VII
THE SCIENCE OF SIGNAL LOCATION

The proper location of signals plays a very
important part in the successful functioning of a traffic
control system. Visibility is the fundamental requirement
in placing signals, since motorists cannot obey signals
if they do not see them. InprOpcrly placed signals
increase the hazard at an intersection instead of lowering
it, since a car proceeding with the green light is likely
to be struck by some ear whose driver failed to see the
red light intended for him. .

Traffic signals can be divided into three classes:

1. Overhead signals suspended on a span wire or on
a mass arm.

2. Pedestal signals mounted within the intersecticnal
area.

3. Post or bracket mounted signals located outside of
the traveled portion of the highway. ‘

Each of these types has a distinct field of
application, and no one type of signal is applicable to
every type of intersection.

The overhead signal, while often considered to
be an inefficient type because of the fact that it cannot
be seen easily by drivers who have stopped while waiting
for the right of way, is nevertheless a highly efficient

type for certain intersections. In many cases it is very

55.

diffith to place any other type of signal so that it can
be seen from a distance so that drivers can tell they are
approaching a signalised intersection. This is especially
true of intersections on state highways. The shoulders of
such highways are often so wide that any type of signal
that must be placed outside the travelable part of the
highway would be likely to be unnoticed by motorists.
Drivers on such highways are in the habit of looking
directly forward at the road, and an overhead signal is
directly in their line of vision.

The pedestal type signal is best adapted to
intersections having a large area. When used, cars should
be taken to make the signal clearly visible to all approaches.
The ideal location for this type of signal is at the Junction
of the center lines of all approaches. In many cases, how-
ever, the intersection is so irregular that no such point
exists, and the signal location must be determined by
experiment. In extreme cases it is necessary to supple
ment the pedestal signal with auxiliary units in order to
show each approach an unmistakable indication.

In many large intersections, drivers have so much
leeway that they are inclined to cut corners and make turns
at an excessive rate of speed. A pedestal signal usually

corrects thiscondition by forcing them to move somewhat

slower through the intersection. In some cases, a pedestal
signal can greatly reduce the danger at an intersection by

forcing some particular turning movement into a very

56.

definite lane, and causing the drivers in this lane to
males the turn slowly and carefully. In a great many
cases a gradual left turn is far more dangerous than a
sharp one, because drivers approaching from the opposite
direction cannot readily decide whether the opposing
traffic intends to turn left or go straight. Such a
method of eliminating the danger due to some particular
flow is justifiable only if it is a very minor movement.

Post or bracket mounted signals are undoubtedly
the best general type to use in traffic control, especially
in cities. Drivers moving through city streets expect to
see traffic signals, and if all signals are located in a
uniform position, the possibility of drivers failing to
see the signal is minimised. Post and bracket mounted
signals provide excellent near visibility and good far
visibility. The choice between bracket munted and post
mounted signals is entirely a local consideration. If
poles already exist at the approximate location that the
signal is to be put, the bracket mounted signal is per-6
fectly satisfactory and does not occupy any additional
sidewalk space. Since.poles do not always exist at the
proper points for signal placement, it is often necessary
to use the post mounted signals. A uniform use of post
mounted signals often adds greatly to the appearance of
the sigmal system, and also to its proper operation, since
the signal can be placed at uniform locations at all

intersections. The far right hand corner is ”contended

57.

as the best location for post or bracket mounted sigials
at most intersections.

In certain cases, special results can be obtained
by placing signals in non-uniform positions. If there is a
heavy left turn movement from one approach of a street, and
a heavy straight through movement from the opposite approach
of a street, it is often possible to make the operation of
the traffic handling system much smoother by placing the
signal for the approach which has the heavy left turn move-
ment on the far corner and the signal for the opposing
approach, which has the heavy straight through movement a
the near corner. This has the effect of stepping the
straight through traffic further back from the intersection,
and the heavy left turn is pcmitted to move into the
intersection in advance of the straight through movement.
This effect can also be obtained by the proper placement
of "Step” lines, but it is very difficult to keep traffic
from running over the "Btop'I line unless the signal is
also placed back from the intersection.

in intersection which requires traffic control
is worthy of the best equipment obtainable, and the item
of cost mould not be weighed too heavily in determining
the type of simals to be used. The installation of a
traffic control system is a capital investment, not an
operating expense, and a system of maxim efficienty will
pay increasingly large dividends to the eonmunity.

58. -

CHAPTER VIII
SWEEIMAYS AND ELEVATED HIGHWAYS

Superhighways.

The superhighway or "Express highway" is grad-
uslly scanning a place of importance in all highway or
traffic systems. The exact form it takes and its relation
to the rest of the highvay system must be carefully worked
out according to the definite needs, the economic situation
and the methods of financing.

There are several exsnples of superhighways now
in existence and several more are being planned. Route 25
in New Jersey is a fine example. It was one of the first
prcjects in such construction and it has more than ful-
filled the upectaticns of its designers.

In Westchester County, New York, the Bronx River,
80 Mill River, and the Hutchinson River Parkways form
main highways to or from metrOpolitan centers.

In Italy superhigheays are called 'sutostrades'.
Tiny have three already constructed and several more
planned.

In Westchester County, New York, right of way
has been acquired for an express highway to be constructed
parallel to the New York, New Haven and Hartford Railroad.
Chicago propost to build a superhighway parallel with the
tracks of the Chicago and Northwestern Railroad for about
ten miles: from the heart of the city to its northwestern

59.

limits.

Detroit has one of the most comprehensive plans
of superhighways. John P. Hallihan, Chief Engineer of the
Detroit Rapid Transit Comission describes this plan very
graphically in his address delivered at the meeting of the
Institute of Traffic Engineers, from which I will quotes
"The facilities that, by reason of obstacles and restric-
tions require in the inner area a two-level street, may be
put in the outer area on a single level, in a street of a
minimum width of 204 feet. A reservation of 84 feet in the
center will provide an exclusive right of way for rapid
transit trains operating on the surface, with stations at
half-mile intervals at separations for cross traffic 3 a
60 foot street flanking the rail reservation on each side
will offer in its final develOpment a two-lane express
motor highway on each side of the rails as well as a two-
lane local roadway and a 15 foot sidewalk. On this thor-
oughfare the local and express motor roadways will be at
the same level at the midpoints between grade separations,
offering easy interchange from one to the other. The
mists cost per mile of this design will average $2,500,000
per mile less than an midst-ground structure for a two-track
line on the two-level thoroughfare.

I "Trunk lines or superhighways of this character
at three mile intervals, with intermediate 130 foot thor-
cughfares at approximate 5 mile intervals, constitute the
preparation that Detroit is making to meet the traffic

60.

problem of the present and of the future. It constitutes
as well the foundation plan for providing the mass trans-
portation facilities required by the expanding city.
"The formal adoption of the Master Plan in 1925
by the City and three Counties was practically coincident
‘ with securing basic legislation designed to effect auto-
matic dedication of right-of-way on subdivision of acreage,
to permit counties to operate through Joint Comissicns in
acquiring right-of-way and, upon definite adoption of the
plan, to impose a preperty tax of one-half mill for its
execution. It has not been found necessary to impose this
special tax. \
"The standard of 120 foot width for main a..-
oughfares is regarded in the Detroit plan as a minimum
requirement in meeting the constantly increasing use of
motor vehicles. Wherever possible to secure a width of
150 feet providing a 30 foot parkway in the centre giving
a boulevard effect, and assisting free movement of traffic
by removing left hand turns from intersections, such
acquisition of right-ofeway will meet with ample Justifi-
cation in the future. The Grand Boulevard in Detroit 11.6
miles long offers an example of the utility of the 150
foot width in its great usefulness as a traffic artery and
its great value in encouraging the highest class of build-
ing development. So, also additional space at intersections

of important thoroughfares permitting round points, or
traffic circles, are of great architectural and real

61.

estate value, besides having the traffic value of per-
mitting continuous movement and eliminating the necessity
of future grade separations for motor traffic.”

Highways Over Existing Streets.

Perhaps, the most successful and most. strateg-
ically located elevated motor highway is the West Side
Elevated Highway now under construction in New York City.
It runs along the Hudson River water front of Manhattan,
utilising a portion of the air rights above the space
composed partly of public streets and partly of the
marginal wharf or place under the jurisdiction of the
Dock Department. Street traffic will still be permitted
to use the space beneath. This highway will provide quick
transportation from downtown to uptown New York.

New York City is also planning a cross-town
express highway which will be a deep-level tunnel passing
beneath all existing or projected rapid transit subways.
It is to be an extension of a midtown vehicular tunnel
under the East River and to connect with a second vehic-
ular tunnel under the Hudson River projected by the Port
of New York Authority. It will have no connections with
the street system except at the two ends - one near
Second Avenue on the East Side and the other near Tenth
Avenue on the West Side. g

In Detroit a 40 foot elevated express toll high-
way has been voted on and approved above the Detroit-

62.

Pontiac Line of the Grand Trunk Western Railway of the
Canadian National System, as part of a $100,000,000 elec-
trification and improvement program. The roadway would be
40 feet above the rails, and intersection highways would
cross on an intermediate level between the railroad and
highway. It 1. proposed to build the highway in sections
and to establish the toll on zone rates.

The consensus of opinion among traffic engineers
seems to be that the elevated highway is not as a rule the
most efficient solution to the traffic problem. It is a
very costly plan as not only the right-of-way must be paid
for but also the settlement of claims of damage to property
because of the deprivation of light, air and access. It is
often necessary to obtain additional width on the surface
level before the construction of elevated roadways becomes
practicable. Since the ultimate aim is to bring more
peeple into the district ahich suffers the most congestion
it has been fomd that superhighwsys offer more relief
than elevated highways. As a high speed artery between
cities of importance the elevated highway serves a real

purpose a

Grade Separations.

If we could eliminate the intersection by means
of separation of gradess we would eliminate the intersection
problem. In the intensively built-up sections the cost
would be staggering and in outlying districts the cost

would not be Justified as a rule. The intersection of two
heavily traveled traffic arteries sometimes justify the
cost of. a grade separation. There are special instances
and locations where grade separation is the only logical
and proper method to employ. In Jersey City it is necessary
to carry the through traffic to the Holland Tubes on a
separate level. In Westchester County, New York the nature
of the country make grade separations the logical method
to use. In Chicago the Lincoln Park Board and the South
Park Csmissioners have built several grade separations.
The ”clover-leaf" intersection on New Jersey
State Route 25 and 4 near Rahway is one of the most com--
plete grade separations ever built. It offers unobstruct-
ed movement along each route and for any turning traffic
between them. This plan requires a great deal of space
mich would make the price prohibitive in a congested

area.

Lsning of Traffic on Superhighways.

With the recent rapid growth of extra-width
highways, it has become increasingly evident that traffic
control methods which are applicable to‘intersections of
narrow highways are not well adapted to intersections
where the clear width of the roadways is in excess of 40
feet. Mile doubling the width of a street or highway
more than doubles its traffic carrying capacity, the

intersections of such broad highways do not show a sorre-

spending increase in traffic handling capacity if they are
controlled by signalling systems which are designed for
narrow streets. Considerable confusion and interference
is caused by cars which turn left from the right-hand lane
or which turn right from the left-hand lane of such wide
thoroughfares.

It has been found in numerous cases that a great
measure of efficiency is gained by dividing traffic into
lanes with respect to the path which it intends to follow
through the intersections. This procedure practically
eliminates the confusion and delay which is usually caused
by uncontrolled turning movemnts-

With traffic preperly lsned with respect to its
destination, it is but a short step to the practice of
signalising each lane separately. In a peat many cases
this procedure permits heavy nonuinterfering traffic flows
to move throughout a large part of the total cycle. In
some cases such flows can be permitted to move continuously.
In other cases, these flows must be stopped during part of
the cycle for the benefit of other. traffic movements which
wish to use the intersection in such a manner that the two
flows would conflict, or it may be neeeseary to stop them
for the benefit of pedestrians.

Excellent results have been obtained by the use
of these methods. The type of signal which has given the
best results in this work is a combination signal and
instruction sigi built into a single unit. The sign is

65.

of the raised glass? letter type, electrically illuminated
at night. In daylight, this type of sign is easily read
without illumination, and is readable from a distance of
several hundred feet, under normal atmospheric conditions,
at all times of the day or night.

One of these signal-sign units is suspended over
each traffic lane. At a normal four-way intersection, the
unit over the rigatehan‘d lane would carry the word uRight".
The unit over the left—hand lane would say ”Left and a
Straight“. In order to fully instruct approaching drivers
as to which lane to enter, overhead signs are placed
approximately 250 feet from the intersection, one over
each lane. These sigma carry brief instructions to
approaching motorists advising them which lane to enter.
The lanes themselves are indicated on the pavement by one
of the customary methods of marking such lines.

It has been found that overhead signals and
instructions signs as described herein are far more effi-
cient in accomplishing a 100% lasing of traffic than an
other method. In heavy traffic, when laning becomes most
important, the drivers attention is on the signal and on
the car ahead of him, and not on the pavement, for this
reason liming instructions painted on the pavement are
very seldom effective. Furthermore, the use of any other
type of signal, such as right or leftturn arroes is much
less efficient than the overhead type. Unless traffic can
be laned nearly 100%, it helps very little to permit cer-

66.

tain movements continuously, since the lanes from which
they should be made are often blocked by cars which have
entered the wrong lane and are waiting for the right-of-
way in the other direction. By permitting the non-inter-
fering traffic flows to move continuously, the accurrmlation
of waiting traffic on the approaches is greatly reduced and
every part of the intersectional area is kept constantly in
use, thereby gently increasing the efficiency of the
system.

In certain cases it is necessary or advisable to
make physical changes in the streets themselves in order
to facilitate the inning process and keep traffic from
entering the srong lane. In cities this entails consider-
able exPense, but it is a comparatively easy matter to
modify state highway intersections in the cpen country,
or city intersections in undeveloPed districts. Changes
which tend to make traffic naturally enter the preper
lane are usually more then paid for by the increased effi-
ciency of control, especially share the traffic density is
high. Comparatively minor changes in the streets often
make it possible to increase the intersectional efficiency
sufficiently so that ma Jor changes such as street widening
projects can be postponed indefinitely. Laned traffic is
an intricate subject and municipalities having problems
for which they are considering landd. control should obtain
the best engineering advice possible.

AN OUTIDOK INTO THE FUTURE.

A survey reveals the fact that methods of
traffic control have shown more improvement in the last
two years than in the preceding ten years. There has been
a great growth in professional activity in the field of
traffic engineering. There is a growing demand for
engineering facts in regard to traffic control and it is
being met with an increase in technical knowledge. It
is also found that the application of sound economic
principles in traffic control is Just as essential as the
application of technical knowledge. ‘

Another cause for this improvement is the fact
that traffic control is being recognised as a technical
rather than a political problem. In 1929 the Mayor of
one of the largest cities in the State of Michigan stated
in a public discussion that a traffic engineer merely
gave a lot of cheap advice and charged an enormous fee ..
that common sense was much better and cheaper. Public
officials of this type must be restrained from interfer-
ing with traffic problems because these problems are of
such nature and magnitude as to warrant the best of
engineering advice.

The Institute of Traffic Engineers was formed
in 1980. In their constitution traffic engineering is
defined as follows: ”Traffic engineering, as used herein,
is defined as the pursuit and determination of pertinent

68.

facts and scientific principles and the application thereof
to the facilitation and control of street and highway
traffic in the interest of safety, convenience and economy".
The leadership and present personnel of this organization _
gives promi se of fine research and disbursement of know.
ledge on traffic problems which has been so meager in the
past. ‘

To definitely predict the traffic control of the
future is an impossible task at'this time. Elevated and
superhighways and the separation of highway grade crossings
will undoubtedly come into more general use. The desip
of intersections will be greatly improved. New Jersey has
done some pioneer work in this field. The Wisconsin State
Higheay Department is constructing several new designs at
the present time. They sill offer non-interfering traffic
a wye with a one way flow. The interfering flows are to
be prevented from turns by boulevards and brought to a
central point where they will be controlled by vehicle
actuated control signals. This desim will net cost much
more to construct than the son-called Cook County desigx
now so commonly used in the Middle West, which fails to
prove the value in the majority of installations. Of
course, the design of intersections inurban areas cannot
be changed as freely as those on the highways. The City
of Milwaukee has redesigned a number of intersections with
the exercise of a goat deal of good Judgment as proved
by the facilitation of traffic movement where these designs-

69.

have been installed.

Signelised intersections seem to offer the most
efficient means of traffic control at the present time
and it seems feasible that they will in the future unless
someinvention unheard of at the present time should enter
the field. The control of these signals can be made very
efficient with apparatus now available. The studies of
Mr. Halsey of the Massachusetts State Highway Department T
have shown the loss of tine imposed on motor vehicles by
using pretimed lights at isolated intersections.
Mr. Johannesson of the New Jersey State Highway Department

in his book entitled "Highway Economics" has sheen what
this delay costs and by capitalizing it Just how much can
be spent economically at each intersection for the relief
of traffic delay. It would appear that research now being
directed towards making pretirned light at isolated inter0
sections more efficient could better be turned toward the
improvement of vehicle actuation, which is fundamentally
sound and offers a much easier solution.

In the control of traffic on heavily travelled
arteries the flexible progressive system seems to give the
best organisation even with expensive delay on the cross
streets. The ideal control would be a progressive wave
controlled by vehicle actuated apparatus so the length of .
each platoon movement could be measured and its speed on
the artery and it would recognise the presence of traffic

'70.

or pedestrians on the intersecting streets. This would
give the artery the uninterrupted freedom of flow found
in the obsolete synchronised system and also the organiza-
tion and speed control of the progressive system.besides
eliminating long delays on the intersecting streets.
Beyond this point it is impossible to predict.
Certainly the prOblem.Iill be solved as efficiently as
others which.have been turned over to American inventive
genius in the past. The final solution will be delayed
only as long as we continue haphazard methods and fail to
give our engineers a.chance and the engineers in turn fail

to examine and put to immediate test all solutions offered.

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