A CASE STUDY ON PERFORMANCE OF TRAFFIC

SIGNAL (RAJKILLPAKKAM JUNCTION)

A MINI PROJECT REPORT

Submitted by

SUKHDEEP SINGH JAT (U12CE117) In partial fulfilment for the award of the degree

Of

BACHELOR OF TECHNOLOGYIN

CIVIL ENGINEERING

DEPARTMENT OF CIVIL ENGINEERING

BHARATH INSTITUTE OF SCIENCE AND TECHNOLOGY

BHARATH UNIVERSITYCHENNAI - 600 073

APRIL 2015

1

ACKNOWLEDGEMENT

It is our duty to show our gratitude to everyone whose magnanimous help and support

motivated us throughout the course of this mini project and made it successful completion

possible.

We express our wholehearted thankfulness to our respected guide Dr.V.Thamizharasan,

Dean & HOD, Dept. of civil engineering for their guidance and innovative propositions

offered right from the very beginning of the project and giving value suggestion and followed

up during the course of the mini project.. They motivated us with the pioneering ideas till the

successful completion of the project.

We wish to express our thanks to all teaching and non-teaching staff of Dept.

of civil engineering for the beneficial help in the accomplishment of this mini project.

Finally we would like to express our deepest gratitude and reverence of our parents

and friends for their steadfast encouragement throughout the progress of this work.

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TABLE OF CONTENTS

CHAPTER NO. TITLE PAGE NO.

1. INTRODUCTION 1

1.1 GENERAL 1

1.2 OBJECTIVES 1

2. THEORETICAL BACKGROUND 2

2.1 ADVANTAGES AND DISADVANTAGES OF 2

TRAFFIC SIGNALS

2.2 SIGNAL INDICATIONS 3

2.2.1 British Practice 3

2.2.2 American Practice 3

2.2.3 Indian Practice 3

2.3 PEDESTRIAN SIGNAL INDICATIONS 3

2.2.1 Flashing Amber 4

2.4 SIGNAL FACE 4

2.5 ILLUMINATION OF THE SIGNALS 7

2.6 AMBER PERIOD, RED/AMBER PERIOD AND 9

INTERGREEN PERIOD

2.6.1 U.K. Practice 9

2.6.2 American Practice 9

2.6.3 Indian Practice 10

2.7 FIXED TIME SIGNALS 10

3

3. LITERATURE REVIEW 12

3.1 ASSESSMENT OF TRAFFIC DELAY PROBLEMS 12

AND CHARACTERISTICS AT URBAN ROAD

INTERSECTIONS

3.2 COORDINATED CONTROL OF TRAFFIC SIGNALS 12

FOR MULTIPLE INTERSECTION

3.3 TRAFFIC FLOW MERGING AND BIFURCATING 13

AT JUNCTION ON TWO-LANE HIGHWAY

3.4 EMPIRICAL DELAYS FORM ACTUATED AND 14

OPTIMISED STATIC SIGNAL SETTINGS COMPARED

3.5 TRAFFIC CHARACTERISTICS OF INDIA 15

3.6 SIGNAL OPTIMIZATION FOR IMPORTANT ROUTES IN 16

NAGPUR CITY

4. DATA COLLECTION 17

4.1 STUDY INTERSECTION 17

4.2 TRAFFIC VOLUME DATA 20

4.3 TRAFFIC COMPOSTION 23

5. ANALYSIS AND RESULTS 25

5.1 THEORY 25

5.2 DESIGN OF SIGNAL TIMING 31

6. SUMMARY AND CONCLUSION 35

6.1 SUMMARY 35

6.2 CONCLUSIONS 35

REFERENCES 36

CHAPTER 1

4

INTRODUCTION

1.1 GENERAL :- The increase in urbanisation and, hence traffic congestion create an urgent

need to operate our transportation systems with maximum efficiency. Real time traffic signal

control is an integral part of modern part of the modern urban traffic control systems aimed at

achieving the optimal utilization of the road network. The use of traffic signal for control of

conflicting streams of vehicular and pedestrian traffic is extensive in most of the towns and

cities. The first traffic signal is reported to have been used in London as early as in 1868 and

was of the semaphore-arm type with red and green lamps for night use. During the hundred

years since then traffic signals have been developed to a high degree of sophistication.

Providing effective real time traffic signal control for a large complex traffic for a network is

an extremely challenging distributed control problem. Signal system operation is further more

complicated by the recent trend that views the traffic signal system as a small component of

an integrated multimodal transportation system.

Optimization of traffic signals and other control devices for the efficient

movement of traffic signals and other control devices for the efficient movement of the traffic

on streets and highways constitutes a challenging part of the advanced traffic management

system of intelligent transportation system.

The urban traffic system is a very complex system which involves many

entities and relationship among them are more complicated. Thus , to setup the system for an

area overwhelming with the traffic needs to be studied and before setting it up. This helps in

the evaluation and the efficiency of the flow through the area and sorts out the correction that

can be applied to optimize the traffic flow.

The study reported here is concerned with the detailed study of a traffic

signal to assess its functional efficiency and to propose corrective measures , if required.

1.2 OBJECTIVES :-

To study the geometric and signal setting features of typical traffic signal.

To study the traffic flow pattern through the signal.

To evaluate the performance of the signal

To prepare corrective measures to improve the performance of the traffic signal.

CHAPTER 2

5

THEORETICAL BACKGROUND

Traffic signals are the means of maintaining an intense flow of traffic in an appropriate way

and to reduce the conflicts at junctions as well as roads. They provide more efficiency if

designed properly.

2.1 ADVANTAGES AND DISADVANTAGES OF TRAFFIC SIGNALS :-

Traffic signals , when properly designed , located and operated , have one or more of the

following advantages:-

They can provide for an orderly movement of traffic.

When proper geometric layouts and control measures are employed , they can

increase the traffic - handling capacity of the intersection.

They can reduce the frequency of certain types of accidents , especially the right-

angle type and pedestrian accidents.

Under favourable condition , they can be coordinated to provide for continuous

movement of traffic at a definite speed along a given route.

They can be used to interrupt heavy traffic at intervals to permit other traffic -

vehicular or pedestrian - to cross.

Traffic signals dispense the with police control and thus can be economical.

If properly designed and set , they can assign right - of - way impartially to traffic ,

unlike manual controls which can stop and interrupt traffic streams at the personal

whim of the traffic controller.

As regard their disadvantages , the following may be mentioned , especially if the signals are

installed improperly :-

Excessive delay to vehicles may be caused, particularly during off- peak hours.

Unwarranted signal installation stands to encourage the disobedience of the signal

indication.

Drivers may be induced to use less adequate and less safe routes to avoid delays at

signals.

Accident frequency , especially of the rear - end type , may increase .

When the installations break down, due to any fault in the system , total and

widespread confusion and difficulties can result.

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2.2 SIGNAL INDICATIONS:-

The types, meaning and sequence of signal indications vary in different countries.

2.2.1 British practice. In British practice, the signal sequence is red, red/amber, shown

together, green and amber. The common practice is to use circular red, amber and green

signals, though in certain circumstances green-arrow signal are also used. When the red

signal is displayed, the right of way is denied to the traffic from entering the intersection. The

red/amber signifies and alert to the drivers that the signal aspect is about to change to green

so that they can be in readiness to go .The green signal aspect denotes that the right of way is

given to the drivers to enter the intersection. The amber signal alerts the drivers that the red

signal aspects is about to commence shortly and green aspect is about to be terminated. A

green - arrow aspect permits the drivers, to enter the intersection to make the movement

indicated by the arrow.

2.2.2 American Practice. In American practices, the signal sequence is red, green and

yellow. Red indication prohibits entry into the section, where as the green permits entry.

Yellow indication warns the traffic that the related green movement is begin terminated and

the red indication is about to commence. Thus, while allowing entry into the intersection

before the yellow aspect requires the traffic to clear the intersection before the yellow

expires. In addition to circular red, green and yellow, American practice permits red arrow,

green arrow and yellow arrow indications to control traffic in certain directions.

2.2.3 Indian Practice. In Indian practice is to have an amber period of 2 seconds as an

transition interval between termination of related green movement and exhibition of red

indication or between termination of a red indication and commencement of related green,

movement.

2.3 PEDESTRIAN SIGNAL INDICATIONS

In U.K. practice, the don't cross cross is given by a red standing man. The cross indication is

a green walking man whereas a flashing green signifies don't start to cross.

7

The Indian Standard on Traffic Signals prescribes the following symbols for pedestrians.

The red standing man represents the don’t cross indication and the green walking man

represents cross indication.

2.3.1 FLASHING AMBER. A flashing amber signal is a hazard identification beacons

normally used to warn of obstruction and intersections to supplement regularity signs and to

warn of midblock cross - walks.

2.4 SIGNAL FACE

The minimum number of lenses in a signal face is three - red, amber and green and the

maximum number in American practice is five. The lenses in a signal face can be arranged in

a vertical or horizontal straight line. The relative position are : red, amber and green. A

simple signal face with three lenses in a vertical line is indicated in the Fig.2.2.

8

Fig.2.1. Pedestrian Signal Indications as per Indian practice

The lenses are normally of two sizes , viz., 200 mm and 300 mm diameter. The larger size is

used where the 85th percentile approach speeds exceed 65 K.P.H. for special problem

locations, for all arrow indication, for intersection where signalisation may be unexpected and

for intersections where drivers may view both traffic control and lane directions control signs

simultaneously. The Indian Standard and the British Standard recommended a size of 200

mm for light signals intended for drivers, 300 mm for green arrow signals and 300 mm for

green signal intended for pedestrian.

The arrows are pointed vertically upward to indicate a straight - through movement and in a

horizontal direction to indicate a turn at approximately right angles. When the angle of the

turn is substantially different from a right angle , the arrow can be positioned an upward

angle approximately equal to that of the turn. The arrow specified in the Indian Standard is

given in Fig.2.3.

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Fig.2.2. Signal Face

Fig.2.3. Standard arrow recommended by Indian Standard

Some of the positions of signals recommended by the Indian Standard are given in Fig.2.4. A

suggested layout of the signal post is given in Fig.2.5.

10

Fig.2.4. Some of the signals permitted by Indian Standards

2.5 ILLUMINATION OF THE SIGNALS

The American practice requires that the signal should be so illuminated as to be visible for a

distance of at least 0.4 km under normal atmospheric conditions. Detailed specifications for

the illumination of the lamps for signals are contained in I.S. 7537-1974.

11

Fig.2.5. Typical layout of traffic signal installations in U.K.

Number and location of Signal Faces

The American practice requires a minimum of two signal faces two be provide and be visible

from a point at least the following distances in advance of and to the stop line :

12Table 2.1.

85 percentile speed ( K.P.H) Minimum visibility (m)

30 30

40 55

50 75

60 100

65 120

75 145

80 170

90 190

100 210

A signal face is, however ,permissible for control of an exclusive turn lane.

Normally one primary signal is installed at 0.9 m from the stop line and a secondary primary

signal is usually installed if there is a central island. A secondary signal is commonly

installed diagonally opposite the first primary signal on the back of the primary signal

intended for the opposing traffic. The typical layout of the traffic signal installation as per

British practice is given in Fig.2.5. The height of the signals according to Indian practice shall

be such that when erected the centre of the amber signals shall not be less than 2.4 m nor

more than 4.0 m above the carriage way level.

2.6 AMBER PERIOD, RED/AMBER PERIOD AND INTERGREEN PERIOD

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2.6.1 U.K. Practice. A typical example of signal indications in a two phase signal as per U.K

practice is shown below.

Fig.2.6. Signal indications in a two phase signal as per U.K. practice.

The amber period is standardised in U.K. as 3 seconds and the red/amber at 2 seconds. The

minimum intergreen period is normally 4 second, but can be increased to suit particular need

such as pedestrian crossing requirements.

2.6.2 American Practice. In American practice, a typical example of signal indications in a

two phase signal is shown in Fig.2.7.

Fig.2.7. Signal indications in a two phase signal as per American practice.

The manual on uniform traffic control devices recommends a yellow intervals of 3 - 6

seconds, longer intervals begin appropriate to higher approach speeds. Sometimes a short all -

14

red clearance interval may be provided immediately after the yellow period to permit the

intersection to clear before cross traffic is released.

2.6.3 Indian Practice. The Indian practice is red, green and amber. The amber interval is

transition interval between termination of related green movement and exhibition of a red

indication or between termination of a red indication and commencement of related green

movement. In the first case it is " Clearance Amber " and in the second case it is called

"Initial Amber". The amber period is generally 2 seconds.

Fig.2.8. Signal indications in a two phase signal as per

In figures 2.6,2.7 and 2.8 the cycle length is indicated. The cycle length is the time required

for one complete sequence of signal indication. Phase is defined as the sequence of the

condition applied to one or more streams of traffic which, during the cycle, receive

simultaneous identical signal indications.

2.7 FIXED-TIME SIGNALS AND VEHICLE-ACTUATED SIGNALS

Fixed time signals are those in which the green periods, and hence the cycle lengths are

predetermined and of fixed duration. Vehicle actuated signals, on the other hand, are those in

which the green periods vary and are related to the actual demands made by traffic. This is

made possible by installing detectors on all the approaches. An intermediate type, semi-

vehicle-actuated signals, is also available, in which the right of way normally rests with the

main road and detectors are located only on the side roads.

15

Vehicle- actuated signals are very popular in U.K, whereas in the U.S.A. fixed time

signals are far more numerous then vehicle-actuated types. The advantages and disadvantages

of the three types are briefly given below :

Type Advantages Disadvantages

1. Fixed Time I. Simple in

construction.

II. Relatively

inexpensive.

III. Most successfully

used in linked

systems requiring a

fixed cycle length for

a given pattern and

speed of progression.

I. Inflexible and hence

may cause avoidable

delay.

II. Require careful

setting.

2. Vehicle Actuated I. They are flexible and

are able to adjust to

changing traffic

conditions

automatically.

II. Delays held to a

minimum and

maximum capacity is

achieved.

I. Require costly

equipment such as

detectors and

sophisticated

controllers.

II. Cannot provide signal

coordination.

3. Semi-vehicle actuated Usually for a junction

of a side street having

low traffic volume

with a main street

having heavy flow.

They are believed to cause

high accident rates at time of

light traffic.

Modern fixed time equipments are built for operation with different settings at certain periods

of the day, to cover different conditions. This is achieved by providing time switches.

CHAPTER 3

16

LITERATURE REVIEW

3.1 Tolu Isaac Atomode (2013) from the Department of Geography , Faculty of Arts and

Social Sciences , Federal University Lokoja, Kogi state ,Nigeria had presented his case study

of Ilorin, Nigeria on "ASSESSMENT OF TRAFFIC DELAY PROBLEMS AND

CHARACTERISTICS AT URBAN ROAD INTERSECTIONS". The traffic delay

problems were manifesting in many of the major urban centres in Nigeria. The paper

examined the traffic delay problem and its causes at selected road intersections in Ilorin,

Nigeria. The characteristics of the intersections that predispose them to delay problem and the

spatial pattern of traffic delay at the road intersections were also identified. In addition, traffic

volume delay characteristics were estimated. Data were collected through direct field surveys

on intersection characteristics , traffic volume, composition delays at the studied

intersections. Also traffic delays are discovered to be associated with the traffic volumes at

various junctions which ultimately translates to traffic congestion. Furthermore , traffic

wardens and parking problems were found to be greatest causes of delays at the road

intersections in the city. Thus this study was made recommending the road intersection to be

signalized and vehicle parking to be prohibited to reduce traffic congestion and delays at road

intersection in the city. This study examined the traffic delay problems at road junction at

road intersections in Ilorin and has offered useful suggestions for improving traffic flow at

junctions.

3.2 Liqiang Fan from (2014) the Department of Information and Computing Science ,

Langfang Teachers University , Langfang, China has studied on the "COORDINATED

CONTROL OF TRAFFIC SIGNALS FOR MULTIPLE INTERSECTIONS". The

proper phase difference of traffic signals for adjacent intersections could decrease the time of

operational delay. Some theorems show how to minimize the total average delay time for

vehicle operating at adjacent intersections under given conditions. If the distance and signal

cycles of adjacent intersections satisfy with specific conditions , the toal average delay time

would achieve zero. If the signal cycles of the adjacent intersections and the phase difference

of them are reducible and the phase difference of them are co-prime numbers , the total

average delay time would be a constant. In general is the signal cycles of adjacent

intersections and the phase difference of them are reducible numbers , the minimum total

average delay time would be solved by the given algorithm. Numerical experiments have

verified the rationality of this theorems. Under the premise of the vehicles driving at the fixed

17

speed on the given roads and some other reasonable assumptions , the vehicle driving on the

roads could achieve minimum total average operational delay by setting phase difference of

traffic signals at the adjacent intersections. This thesis gives the minimum average delay time

under the conditions that the cycles of traffic signals meet the different finite conditions. In

particular , if the cycles of signals at adjacent intersections are co-prime numbers.

3.3 Kazuhiro Tobita, Yuichi Naito, Takashi Nagatani of Department of Mechanical

Engineering , Division of Thermal Science, Shizouka University , Hamamatsu, Japan

provided a report on "TRAFFIC FLOW MERGING AND BIFURCATING AT

JUNCTION ON TWO-LANE HIGHWAY". They had studied the traffic states and jams

in vehicular traffic merging and bifurcating at a junction on a two-lane highway. The two-

lane traffic model for the vehicular motion at the junction is presented where a jam occurs

frequently due to merging, lane changing, and bifurcating. The traffic flow is called the

weaving. At the weaving section, vehicles slow down and then move aside on the other lane

for changing their direction. They derive the fundamental diagrams (flow-density diagrams)

for the weaving traffic flow. The traffic states vary with the density, slowdown speed, and the

fraction of vehicles changing the lane. The dynamical phase transitions occur. It is shown that

the fundamental diagrams depend highly on the traffic states. They had investigated the

traffic states and dynamical phase transitions in the merging and bifurcating traffic flow

(weaving traffic) at the junction on a two-lane highway. They had presented the dynamical

traffic model mimicking the weaving traffic at the junction. They had derived the

fundamental diagrams (current-density diagrams) for the traffic flow on the weaving traffic.

They had shown that there are four distinct traffic states and the traffic flow changes to the

distinct states through three dynamical transitions. They had found the condition such that

vehicles changing the direction are successful to sort themselves into their respective lanes.

They had clarified that the traffic flow depends highly on the vehicular density, the slowdown

speed, and the fraction of vehicles changing the direction.

The study will be the first to discuss whether the junction works successfully on a two-lane

highway for the merging and bifurcating vehicles and to clarify the dependence of successful

weaving traffic on the slowdown speed. This work will be useful to operate efficiently the

junction on the highway.

18

3.4 Johnnie Ben-Edigbe and Iffazun bt Mohd Ibrahim (2010) studied on the "EMPIRICAL

DELAYS FORM ACTUATED AND OPTIMISED STATIC SIGNAL SETTINGS

COMPARED". Many intersections have varying mechanism for vehicles right of way as

they approach the intersection. With actuated signal, induction loops buried in the roadway

stop-line, video, infrared or microwave detection system automatically adjusts timings

relative to prevailing degree of saturation. An intersection without such detection system

operates on fixed times (static). Signal settings are based on fixed proportional distribution of

effective green per cycle time. In the paper, daylight and dry weather traffic performances at

standalone signalised 4-way intersection were investigated under actuated and optimised

signal timing conditions. Based on the hypotheses that peak traffic performance at standalone

between optimised static and actuated signal settings are insignificant; discharge rates, delays

and effective green timings for both were estimated compared and contrasted. Given that an

optimised static signal assigns predetermined time irrespective of traffic demand; saturation

flows were fixed at 1900 for straight, 1800 left turning and 1700 right turning vehicles per

hour per lane respectively. Results show marginal differences in peak period effective green,

discharge rates and delays. The paper concluded that optimised static signal can produce

good results and should also be considered especially at standalone intersections where traffic

operations are at peak regularly.

In their evaluation for signalized intersection performance, three measures are commonly

used flow ratios, delay and queue. Based on the hypothesis that, optimised static signal is just

as effective as a fully actuated signal system and also the findings from their study, they

concluded that:-

Difference in effective green time between fully actuated and optimized static signal

timing is minimal;

Difference in delay per vehicle between fully actuated and optimized signal timings is

significant;

The level of service at standalone intersection from optimized static and fully actuated

signal system is the same;

The choice of signal setting is dependent on the intersection of interest and its traffic

characteristics; and

The assertion that optimised static is not as effective as fully actuated signal system is

null and void.

19

3.5 Dr. Santosh A.JALIHAL(Scientist, E-1) , Dr.T.S. Reddy (Director Grade Scientist) ,

KAYITHA Ravinder (Doctoral Student) (2005) Traffic Transportation Planning And

Engineering Central Road Reaserch Institute , New Delhi published the report on "TRAFFIC

CHARACTERISTICS OF INDIA". The revolution in the automobile industry and

liberalised economy has led to tremendous increase in the vehicle ownership levels. This has

resulted in changing traffic characteristics on road network. In their paper an attempt has

been made to analyse the changing traffic composition trends, speed characteristics and travel

patterns by taking few case studies. Further, the impact of changing traffic composition

trends and emerging issues thereof are has been discussed in the published report.

From the previous sections it can be inferred that in all the cities studied there is significant

shift from the share of cycles towards fast moving vehicles i.e. two wheelers and cars,

irrespective of the location in the city. Further, in the past decade the share of cars is

increasing as compared to two wheelers. Generally it was found that the share of public

transport (buses) is declining. These changes in traffic composition will have varying impact

on the operation and management of traffic, which are discussed below. The traffic

composition has changed drastically over period of time in all the cities of Delhi. In general

the shift is towards personal modes of travel such as two wheelers and cars. Therefore,

emphasis should be given to address the following issues:

Speed of Operation: Generally the homogeneity of traffic improves the speed of

operation on the roads which further influences the geometric design aspects.

Safety: The increasing speeds would result in reduced safety especially in core areas

where pedestrian and vehicular conflicts are more.

Capacity of Roads: The increasing growth of fast moving vehicles will require

improved capacity of roads to accommodate growing traffic, maintain required level

of service and efficiency.

Infrastructure Facilities: The shift towards cars, two wheelers, auto rickshaws and

taxies will require appropriate facilities like parking spaces and auto/taxi stands etc. to

be developed.

Traffic Control at Signals: The traffic controls at signals in the road network of the

cities require to be redesigned to accommodate the changing traffic.

Segregation of Traffic: In order to increase safety and efficiency of traffic operation

the fast moving vehicles and slow moving vehicles need to be segregated.

20

Hierarchical Road System: The increasing trend towards fast moving vehicles would

require well defined hierarchical road system (Arterial, Collector/Distributors and

Access Roads) to be developed in the cities for faster and safe movement of traffic.

3.6 Kishore Bambode , Vishal Gajghate (2014) ( G.H. Raisoni College of Engineering ,

Nagpur) published the report on "TRAFFIC SIGNAL OPTIMIZATION FOR

IMPORTANT ROUTES IN NAGPUR CITY". In India number of vehicles are increasing

day by day hence major cities in India like Nagpur facing to so many problems such as loss

of time, increased in fuel consumption, increase in noise pollution and it caused long queues

which produce inconvenience , frustration to drivers or road users. The city Nagpur have too

many intersections and too many traffic signals. It rely on pre timed control signal system or

fixed cycle control signal system hence it is beneficial to optimize traffic signal and

coordinated it by means of Intelligent transportation system. It is not yet adopted on Indian

roads. This paper presents an intelligent transportation system for traffic flow prediction and

control it through traffic signal optimization and coordination. The intersection is one of the

most important parts in traffic network. It is act like the key node in for avoiding traffic

congestion so the intersection control study is attracting more and more researcher’s

attention. Signal optimization is very effective techniques for improving intersection level of

service and make it more efficient.

CHAPTER - 4

21

DATA COLLECTION

4.1 STUDY INTERSECTION

Intersection for the case study - Rajkilpakkam Junction is located on Velachery Tambaram

road in the southern part of Chennai city.

As per the need of the case study at the junction data on the following aspects were collected.

Signal Cycle Timing.

Volume of different category of vehicles moving through intersection.

Composition of all the types of vehicles per hour as per the video captured data.

The layout of the intersection is shown in Fig.4.1. The traffic flow details during the

different phases of the signal.

Fig.4.1.(layout of the intersection)

Flow Diagram

22

Fig.4.2. (a) Traffic flow in Phase I

Fig.4.2. (b) Traffic flow in Phase II

Fig.4.2. (c) Traffic Flow at Phase III

23

The signal timings details of morning and evening peak hours followed at the

intersection are shown in Fig.4.3. and Fig.4.4.

Fig.4.3 Signal Timing Diagram ( Morning Peak Hour)

Fig.4.4. Signal Timing Diagram ( Evening Peak Hour)

24

4.2 TRAFFIC VOLUME DATA

The traffic data of the study intersection was collected during the morning and evening peak

hours by video capturing the traffic flow. The video captured traffic data was then transferred

to computer for classified count of vehicles. Since the traffic on Indian road is heterogeneous

it is necessary to count the different types of vehicles into equivalent Passenger Car Unit

(PCU). The PCU values used to convert the different types of vehicles are given in Table 4.1.

The PCU vales of the different types of vehicles adopted for the survey are

shown in Table 4.1.

Table 4.1. PCU Values of Vehicles

Sno. Vehicle Type PCU values

1. Truck 2.2

2. Bus 2.2

3. Articulated 3.2

4. LCV Goods 1.4

5. LCV Passengers 1.4

6. Cars 1

7. Two Wheelers 0.35

8. Three Wheelers 0.7

9. Bicycle 0.35

10. Tricycle 0.7

The traffic volume data of the intersection was collected by conducting field

survey using video camera. The data of the traffic volume composition of

morning and evening peak period shown in Tables 4.2 and 4.3 respectively.

Table 4.2. Traffic Data of Morning Peak Period

25

Table 4.3. Traffic Data of Evening Peak Period

26

4.3 TRAFFIC COMPOSITION

27

The details of the percentage composition of the traffic observed at the intersection during the

morning and evening peak periods are shown in Fig.4.5 and Fig.4.6 respectively.

Truck0%

Bus3%

Articulatd1%

LCV Goods7%

LCV Passengers3%Cars

22%

Two Wheelers58% Three Wheelers

5%

Bicycle 1%

Tricycle0%

TRAFFIC VOLUME COMPOSTION

TruckBusArticulatdLCV GoodsLCV PassengersCarsTwo WheelersThree WheelersBicycle Tricycle

Fig.4.5. Traffic composition during Morning Peak

28

0%2% 0%

3%4%

32%

53%

4%1%

0%

TRAFFIC VOLUME COMPOSITION

Truck

Bus

Articulatd

LCV Goods

LCV Passengers

Cars

Two Wheelers

Three Wheelers

Bicycle

Tricycle

Fig.4.6. Traffic Composition during Evening Peak

29

CHAPTER - 5

ANALYSIS AND RESULTS

5.1 THEORY

The subject of determination of Optimum Cycle Length and Signal Settings for an

Intersection with Time Signals was studied in the Road Research Laboratory (U.K.) by

means of computer simulation of flow at traffic signals. The result used in determining the

compromise cycle time that would suit variations in flow during the day.

By differentiating the equation for the total delay for intersection with respect to cycle time,

the following equation for the optimum cycle time has been obtained :

Co=1. 5 L+5

1−Yseconds .........................................(1)

where Co = optimum cycle time

L = lost time per cycle ( in seconds)

Y = y1+y2+................+yn

and y1,y2........,yn are the maximum ratios of flow to saturation flow

. for phases 1,2......n ( i.e., q/s where q is the flow and s is the

saturation flow ).

The lost time L in the above formula can be understood with reference to Fig.5.1 , indicating

the rate of flow against time.

Fig.5.1. Rate of flow against time.

30

The figure of rate of flow against time shows that as soon as the green signal is given , the

rate of discharge begins to pick up and some time is lost before the flow reaches the

maximum value ( saturation flow ). Similarly at the termination of the green phase, the flow

tends to taper off , involving a further lost time. The lost time for the phase would then be :

l = k + a - g.........................................(2)

where l = lost time for the phase

k = green time for the phase

a = amber time for the phase

g = effective green time = b/s

b = number of vehicles discharged on the average during a

saturation flow

s =saturation flow

The total lost time due to starting delays per cycle with be nl if there are n phases in the cycle.

In addition to this lost time , the time R during each cycle when all signals display red

(including red/amber) simultaneously is also lost to traffic. Thus the total lost time L can be

expressed as :

L = nl + R..............................(3)

The value of Y is the sum of y values for each phase. Each phase will handle one or more

intersections , each approach having its own traffic flow and saturation flow. But for the

purposes of the above formula , it has been shown by Webster that the y value for the phases

may be taken as the highest ratio of traffic flow to saturation flow.

31

The effective green time available in a cycle can be apportioned to the different phases by

following rule, so as to give the least overall delay to the traffic using intersection :

g1 : g2 .................gn = y1:y2.................:yn

where

g1,g2,......gn = effective green times allotted to phases 1,2......,n

respectively.

y1,y2........yn = maximum of y values

(=Flow /Saturation flow = q/s) for phases 1,2,........n

respectively.)

The optimum cycle time obtained from equation (1) may be very short under light traffic

conditions. From particle considerations the lower limit of the cycle time may taken as 25

seconds. The upper limit may be regarded as 2 minutes.

Saturation Flow. In determining the y value , the saturation flow should be measured rather

than estimated value . The method of measuring the saturation flow is described in an RRL

publication . For designing new signal installations , the following simple formula devised by

the Road Research Laboratory U.K. can be used :

s = 525 w PCU/hour .............................(4)

where, s = saturation flow

w = width of approach road in metres measured kerb to inside of

pedestrian refuge or centre line, whichever is nearer , or to the inside of the central

reserve in case of a dual carriageway.

The above formula is valid for widths of from 5.5 to 8 m. For lesser with the values may be

obtained from table 5.1.

32

Table 5.1 Saturation Flow for Widths 3 to 5.5

When the approaches are in a gradient, the saturation flow needs some adjustment. Approximately

this can be done by decreasing the saturation flow by 3% for each 1% uphill gradient and

increasing the saturation flow by 3% for each 1% of downhill gradient.

The effect of composition of vehicles can be accounted for in measuring the flow and saturation

flow by converting into PCU equivalent as for values given in table 5.2.

Table 5.2 PCU Equivalent

Types of Vehicles PCU Equivalent

Truck 2.2

Bus 2.2

Articulated 3.2

LCV Goods 1.4

LCV Passengers 1.4

Car 1

Two Wheelers 0.35

Three Wheelers 0.7

Bicycle 0.35

Tricycle 0.7

PCU Equivalents for Traffic Signal Composition

The effect of right-turning traffic on the saturation flow can be accounted for in the following

manner:

No opposing flow, no exclusive right-turning lanes. An overall figure of saturation flow for

the approach , irrespective of turning movements , can be obtained using the rules given

below.

33

Width w in

metres

3.0 3.5 4.0 4.5 5.0 5.5

S (PCU/hour) 1850 1890 1950 2250 2250 2900

No opposing flow, exclusive right-turning lanes. The saturation flow of right-turning

stream through a right-angle should be obtained separately by the following formula:

s=1800

1+1 .52 /r PCU/hour for single file stream

and s=3000

1+1 .52 /r PCU/hour for single file stream

where r is the radius of curvature (in metres) of the right turning stream through a right

angle.

Opposing flow, no exclusive right turning lanes. Three effects are possible under this

circumstances. Firstly, because of the opposing traffic, the right turners are

themselves delayed and consequently delay other non-right-turning vehicles in the

same stream. Secondly, their presence tends to inhibit the use of the off-side lane by

straight ahead vehicle. These two effects can be allowed by assuming that on the

average each right-turning vehicle is equivalent to 1.75 straight ahead vehicles. The

third effect pertains to the discharge of right-turners through suitable gaps in the

opposing stream. The following equation gives the maximum number of right-turning

vehicles per cycle (nr) that can take advantage of gaps in the opposing stream:

nr=sr ×( g s−qcs−q )

where sr = right turning saturation flow

g = green time

c = cycle time

q = flow in opposing arm

s = saturation flow for opposing arm.

If g and c are in seconds in the above equation, s should be flow per second.

34

If the average number of right-turners per cycle is more than nr , the difference between the

two (nw) will have to wait at the intersection at the termination of the green time. For

allowing all these nw vehicles to clear the intersection, the intergreen time can be made equal

to 21/2 nw hours seconds, assuming each vehicles takes 21/2 seconds to clear.

Opposing flow, exclusive right-turning lanes. . There will be no delay to the straight

ahead traffic using the same approach as the right turners, but there will be an effect

on the cross-phase and this should be calculated as outlined above.

The effect of the left tuners on the saturation flow can be disregarded if the percentage of left

turners is less than 10. If more, a correction is made for the excess of over 10 percentage by

assuming each left turner is equivalent to 1.25 straight ahead vehicles.

The effect of site characteristics cab be considered by applying the factors given in table5.3.

Table 5.3 Effect of Site Characteristics on Saturation Flow

Site Designation Description Percentage of standard

saturation flow

Good Dual carriageway. No

interference from

pedestrians , parked vehicles,

right-turning-traffic, (either

owing to their absence or

because special provision is

made for them). Good

visibility and adequate

turning radii.

120

Average Average sites. Some

characteristics of 'Good' and

'Poor'.

100

Average speed low. Some

interference from standing

vehicles, pedestrians, right

turning traffic. Poor visibility

and/or poor alignment of

85

35

intersection. Busy shopping

street.

5.2 DESIGN OF SIGNAL TIMING

For Morning Peak data

from equation (1),

Co=1.5 L+5

1−Yseconds

we have, L = 6 seconds ( lost time per cycle )

considering the saturation to be high,

taking, s = 650 w PCU/ per hour

therefore,

o For phase I,

s = 650 X 10 = 6500 PCU/per hour

o For Phase II,

s = 650 X 9 = 5850 PCU/per hour

o For phase III,

The width of the road occupied by the vehicle is considered to be 5 m whose

saturation value is provided accordingly to equation 4 (Refer. Table.5.1) and

hence the saturation value has to be increased as per observation by 650.

Therefore,

s=( 2250 ×650525 )×5 = 13929 PCU/per hour

Now ,

Y = y1+y2+y3............... (since it's a three phase signal)

where, y is the ratio of actual flow to saturation flow.

i.e.,

y=qs

36

o For Phase I,

y1=29076500

=0 . 44

o For Phase II,

y2=22675850

=0 . 38

o For Phase III,

y3=914

13929=0 .065

Therefore, Y = 0.44 + 0.38 + 0.065

Y = 0.885

From equation (1)

Co=(1 .5× 6)+5

1−0.885seconds

Co=122 seconds

Therefore , the total effective green time can be given as

¿(Co−L)seconds

¿122−6

= 166 seconds

Effective green time for each phase,

where, g=y1

Y× totaleffective green

o For Phase I,

g1=0 .44

0 . 885× 116=58 seconds

o For Phase II,

g2=0 .38

0 . 885× 116=50 seconds

37

o For Phase III,

g3=0 . 0650 . 885

× 116=9 seconds

However, provide a minimum green time of 15 seconds. Thus, taking g3 as 15

seconds. The total cycle time by providing 3 seconds for amber is found to be 132

seconds.

Fig.5.1. Timing Diagram (Morning Peak)

For Evening Peak data,

from equation (1),

Co=1.5 L+5

1−Yseconds

we have, L = 6 seconds ( lost time per cycle )

considering the saturation to be high,

taking, s = 650 w PCU/ per hour

therefore,

o For phase I,

s = 650 X 10 = 6500 PCU/per hour

o For Phase II,

38

s = 650 X 9 = 5850 PCU/per hour

o For phase III,

The width of the road occupied by the vehicle is considered to be 5 m

whose saturation value is provided accordingly to equation 4 (Refer. Table.5.1)

and hence the saturation value has to be increased as per observation by 650.

Therefore,

s=( 2250 ×650525 )×5 = 13929 PCU/per hour

Now ,

Y = y1+y2+y3............... (since it's a three phase signal)

where, y is the ratio of actual flow to saturation flow.

i.e.,

y=qs

o For Phase I,

y1=43656500

=0 .67

o For Phase II,

y2=40795850

=0 .69

o For Phase III,

y3=1466

13929=0 . 105

Therefore, Y = 0.67 + 0.69 + 0.105

Y = 1.465

Since, the Y¿1 therefore to design cycle time for evening the road should be made wide.

39

CHAPTER - 6

SUMMARY AND CONCLUSIONS

6.1 SUMMARY

The traffic signals are important traffic control devices that determine the functional

efficiency of urban road network. Hence , design of traffic signals is very important to see

that the delay caused to vehicles at the signals is minimum. The study is concerned with the

assessment of the functional efficiency of a traffic signal located on an Urban arterial road

(Velachery - Tambaram road ) in the other part of the Chennai city.

For the purpose of the study of existing roadway and traffic condition at the study

intersection was first studied. Then, appropriate corrective measures to improve the

efficiency of the traffic signal were proposed.

6.2 CONCLUSIONS

The following are the important and corrections of the study :

I. The traffic at the study intersection is highly heterogeneous with a mix of vehicles

with wide ranging and dynamic characteristics.

II. The current signal timing during the morning peak has a cycle length of 140 seconds.

III. The present signal timing for the evening peak period has a cycle length of 148

seconds.

IV. The redesign of the signal time for the morning peak has resulted in a cycle time of

132 seconds - 8 seconds less than the field observed time of 140 seconds.

V. The present cycle time for the evening peak results in long queue of vehicles at the

traffic takes more one cycle to draw the intersection. Hence, it is necessary to widen

the approach to the road to improve the performance of the signal.

40

REFERENCES:

1. Liqiang Fan, ( Department of Information and technology ), Langfang Teachers

University, China, " Coordinated Control of Traffic Signals for Multiple

Intersections". (Published on 1 June 2014)

2. Tolu Isaac Atomode, Department of Geography, Faculty of Arts and Social

Sciences, Federal University Lokoja, P.M.B 1154, Lokoja, Kogi State, Nigeria,

Volume 12, Issue 4 (Jul. - Aug. 2013), PP 06-16.

3. Kazuhiro Tobita, Yuichi Naito, Takashi Nagatani ( Department of Mechanical

Engineering, Division of Thermal Space, Shizouka University , Hamamatsu,

Japan(2012). (Published on 27 June 2012)

4. Kishor Bambode, Vishal Gajghate , G. H. Raisoni College of Engineering, Nagpur

(India), (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2,

February 2014).

5. Dr. Santosh A.JALIHAL(Scientist, E-1) , Dr.T.S. Reddy (Director Grade

Scientist) , KAYITHA Ravinder (Doctoral Student) ,Traffic Transportation Planning

And Engineering Central Road Reaserch Institute , New Delhi , Proceedings of the

Eastern Asia Society for Transportation Studies, Vol. 5, pp. 1009 - 1024, 2005.

6. Johnnie Ben-Edigbe and Iffazun bt Mohd Ibrahim , Department of Geotechnic

and Transportation, Universiti Teknologi Malaysia, ISSN 1819-6608, VOL. 5, NO. 1,

JANUARY 2010

7. L.R. Kadiyal , Traffic Engineering and Transport Planning, Khanna Publications.

41