A presentation telling about the work done and the how the result obtained and mathematical explanation for designing.

1. A CASE STUDY ON PERFORMANCE OF TRAFFIC SIGNAL
A PROJECT REPORT
submitted
by
SUKHDEEP SINGH JAT (U12CE117)
Under the Guidance of –
Dr. V. Thamizharasan

2. Introduction
 The use of traffic signals for control of conflicting streams of
vehicular and pedestrian traffic is extensive in most of towns and
cities.
 The first traffic signal is reported to have been used in London
as early as in 1868.
 The urban traffic system is a very complex system which
involves many entities and relationship among them and are
more complicated.
 Thus, to setup the system for an area the traffic volume needs to
be studied before setting it up.
 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.

3. 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.

4. Data Collection
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.

5. The layout of the intersection is shown in Fig.1. The traffic flow
details during the different phases of the signal.
Fig.1.(layout of the intersection)

6. Flow Diagram
Fig.2. (a) Traffic flow in Phase I

7. Fig.2. (b) Traffic flow in Phase II

8. Fig.2. (c) Traffic Flow at Phase III

9. The signal timings details of morning and evening peak hours
followed at the intersection are shown in Fig.3. and Fig.4.
Fig.3 Signal Timing Diagram ( Morning Peak Hour)

10. Fig.4. Signal Timing Diagram ( Evening Peak Hour)

11. 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 1.
The PCU vales of the different types of vehicles adopted for the
survey are shown in Table 1.

12. Table.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

13. • 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 2 and 3 respectively.

14. Table 2 Traffic Data of Morning Peak Period

15. Table 3 Traffic Data of Evening Peak Period

16. Traffic Composition
The details of the percentage composition of the traffic observed at the intersection during
the morning and evening peak periods are shown in Fig.5. and Fig.6. respectively.
Truck
0%
Bus
3%
Articulatd
1%
LCV Goods
7%
LCV Passengers
3%
Cars
22%
Two Wheelers
58%
Three Wheelers
5%
Bicycle
1%
Tricycle
0%
TRAFFIC VOLUME COMPOSTION
Truck
Bus
Articulatd
LCV Goods
LCV Passengers
Cars
Two Wheelers
Three Wheelers
Bicycle
Tricycle
Fig.5. Traffic composition during Morning Peak

17. Truck
0%
Bus
3%
Articulatd
0%
LCV Goods
3%
LCV Passengers
4%
Cars
32%
Two Wheelers
53%
Three Wheelers
4%
Bicycle
1%
Tricycle
0%
TRAFFIC VOLUME COMPOSITION
Truck
Bus
Articulatd
LCV Goods
LCV Passengers
Cars
Two Wheelers
Three Wheelers
Bicycle
Tricycle
Fig.6. Traffic Composition during Evening Peak

18. Analysis and Results
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 :
...... ...................................(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 ).

19. The lost time L in the formula can be understood with reference to Fig.7 , indicating the
rate of flow against time.
Fig.7. Rate of flow against time

20. 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 4.
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
Table.4 Saturation Flow for Widths 3 to 5.5

21. 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.
Table.5 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

22. Design of Signal Timing
• For Morning data
from equation (1),
we have, L = 6 seconds ( lost time per cycle )
considering the saturation to be high,
taking,
s = 650 w PCU/ per hour

23.  For phase I,
s = 650 X 10 = 6500 PCU/per hour
 For Phase II,
s = 650 X 9 = 5850 PCU/per hour
 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,
= 13929 PCU/per hour

24. 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.,
For Phase I,
For Phase II,
For Phase III,
Therefore,
Y = 0.44 + 0.38 + 0.065
Y = 0.885

25. From equation (1)
Therefore , the total effective green time can be given as
= 166 seconds

26. Effective green time for each phase,
where,
• For Phase I,
• For Phase II,
• For Phase III,
However, provide a minimum green time of 15 seconds. Thus, taking
as 15 seconds. The total cycle time by providing 3 seconds for amber
is found to be 132 seconds.

27. Timing Diagram (Morning Peak)

28. For Evening Peak data,
from equation (1),
we have,
L = 6 seconds ( lost time per cycle )
considering the saturation to be high,
taking,
s = 650 w PCU/ per hour

29. Therefore,
 For phase I,
s = 650 X 10 = 6500 PCU/per hour
 For Phase II,
s = 650 X 9 = 5850 PCU/per hour
 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.4.) and hence the saturation value has to be
increased as per observation by 650.
Therefore,
= 13929 PCU/per hour

30. 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.,
For Phase I,
For Phase II,
For Phase III,
Therefore, Y = 0.67 + 0.69 + 0.105
Y = 1.465
Since, the actual flow of traffic is more than the saturation flow
therefore to design cycle time for evening the road should be made
wide.

31. Conclusions
The following are the important and corrections of the study :
The traffic at the study intersection is highly heterogeneous
with a mix of vehicles with wide ranging and dynamic
characteristics.
The current signal timing during the morning peak has a cycle
length of 140 seconds.
The present signal timing for the evening peak period has a cycle
length of 148 seconds.
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.
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.

32. REFERENCES:
Liqiang Fan, ( Department of Information and technology ),
Langfang Teachers University, China, " Coordinated Control of
Traffic Signals for Multiple Intersections". (Published on 1 June
2014)
 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.
Kazuhiro Tobita, Yuichi Naito, Takashi Nagatani (
Department of Mechanical Engineering, Division of Thermal
Space, Shizouka University , Hamamatsu, Japan(2012).
(Published on 27 June 2012)

33. 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.
 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
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).
L.R. Kadiyal , Traffic Engineering and Transport Planning,
Khanna Publications.