The document outlines the design of a two-phase traffic signal system at S.R. Nagar Community Hall using the Webster method, focusing on optimizing cycle time and allocating green time based on traffic volume data. It includes historical context, terminology, and methodology for traffic signal design, as well as findings from data collection indicating peak traffic volumes. The study concludes that implementing traffic signals will enhance safety and efficiency in traffic movement at the specified junction.

1. BY
U. SAMADHANA
4/6/2022
1
DESIGN OF A TRAFFIC SIGNAL AT
S.R. NAGAR COMMUNITY HALL

2. ABSTRACT
In this project we mainly focus on design of a two phase signal system
by Webster method. Besides it also deals with necessity and
importance of various types of traffic signals along with the
terminology which are involved in the design. As a part of project we
have noted the classified vehicular count at S.R. Nagar Community
Hall to implement a traffic signal at this location.
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3. OBJECTIVES
 Determination of optimum cycle time.
 Finding the peak hour volume.
 Determining the peak period of traffic flow.
 Study on classified volume counts.
 Allocation of green time for roads based on webster method.
 Designing a traffic signal by Webster method.
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4. • INTRODUCTION
A traffic light, traffic signal, or stop light is a signaling device
positioned at a road intersection, pedestrian crossing, or other
location in order to indicate when it is safe to drive, ride, or walk
using a universal color code.
However for the pedestrians, there have only two lights, a red
light and a green light that mean go and stop respectively. The traffic
lights have given many benefits to all road users. Besides reducing
the number of accidents, it made the traffic flow smoothly and
possibly could save people time.
The second paragraph with red doesn’t have proper meaning
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5. TERMINOLOGY
 Cycle
The appearance of red, amber, green signals.
 Cycle length
The time in seconds that it takes a signal to
complete one full cycle of indications.
 Change interval
Change interval is also called the yellow time
indicates the interval between the green and red signal
indications for an approach.
 Clearance interval
The time interval for clearing off the vehicles in
the intersection.
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6.  Green interval
The actual duration for which the green light of a traffic
signal is turned on.
 Red interval
The actual duration for which the red light of a traffic
signal is turned on.
 Phase
A phase is the green interval plus the change and
clearance intervals that follow it. It allows a set of
movements to flow and safely halt the flow before the phase
of another set of movements start.
 Lost time
The time during which the intersection is not
effectively utilized for any movement.
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7.  Cycle time
The time taken by a signal to complete one full
cycle of iterations. I.e. one complete rotation through
all signal indications.
 Effective green time
The actual time available for the vehicles to cross
the intersection.
 Lane capacity
It is the ratio of effective green time to the cycle length.
 Critical lane
The lane which has the heavy flow of traffic in any
phase.
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8. TYPES OF TRAFFIC SIGNALS
1. Traffic control signal
a. Fixed – time signal
b. Manually operated signal
c. Traffic actuated signal
2. Pedestrian signal
3. Special Traffic signal
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9. HISTORICAL BACKGROUND
&
LITERATURE REVIEW
• In 1722, at London Bridge three men were appointed to control
the flow of traffic.
• On 9th December 1868, the first, non-electric, gas-lit traffic lights
were installed outside the Houses of Parliament in London to
control the traffic and was proposed by the railway engineer J. P.
Knight.
• In the first two decades of the 20th century the words “Stop” and
“Go” were in white on a green background and the lights had red
and green lenses illuminated by kerosene lamps.
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10. • In 1920, the first three-color (amber) traffic light was created
by an police officer William Potts in Detroit, Michigan.
• In 1922, traffic pole have been installed to control the traffic
by automatic timers.
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11. • In 1953, South India first traffic light was installed at
Egmore Junction, Chennai.
• In 1967, the city of Toronto was the first to use more
advanced computers that were better in controlling the
flow of traffic.
• In 1990’s countdown timers were introduced on traffic
lights.
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12. • Robert B. Noland in 1996 designed the traffic signal to
improve traffic flow and concluded that green phases for
pedestrians should be shortened only when vehicle volumes
are greater.
• Khiang Tan et al in 1996 developed graphical software for
design and implementation of an automatic traffic light and
concluded that this is high in terms of performance and cost.
• Karthik et al in 2012 proposed a system to analyze the live
camera recording to handle the traffic data and allocated the
optimal time for the vehicles to pass in the intersection.
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13. • Rekha & karthika in 2013 studied on different types of
vehicle sensors used for automatic traffic signal control
and proposed loop sensors for allotment of green time to
clear traffic and found it effective in handling the traffic.
• G. Krishnaiah in 2013 studied on traffic signal control
system and concluded that through wireless traffic control
system there will be an easy acess for the flow of traffic
on the road.
• Hussian in 2013 proposed the concept of wireless sensors
network to have the real time traffic data to clear off the
traffic at an intersection and proved it more efficient in
mixed traffic conditions.
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14. • Vidhya&Bhanu in 2014 developed a density based traffic
signal design and allocated the green time to the road
stretch with more traffic so that vehicles flow through the
intersection more easily.
• Krity Kumari in 2014 studied on density based traffic
design system and concluded that by providing the sensors
along the road the time of the traffic lights can be assigned.
• Hrairi in 2014 studied on development of sensor based
traffic light system and concluded that by increasing the
number of sensors to detect the presence of vehicles at the
intersection the signal length can be changed.
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15. • Ahmed Hassan et al in 2014 studied on design of semi- automatic
traffic light control system and concluded that by the intelligent
traffic control system we can avoid the traffic jams.
• Yao Wu et al in 2015 studied on development of an optimization
traffic signal cycle length model for signalized intersections and
concluded that this gives a more optimal model as it took the
different traffic conditions at the intersection.
• Michal in 2016 studied on design and development of an improved
traffic light control system using hybrid lighting system there will be
high luminosity and capability of gaining driver attention in real-
time.
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16. Two phase signals
 Two phase system is usually adopted if through
traffic is significant compared to the turning movements.
 For example an non-conflicting through traffic 3
and 4 are grouped in a single phase and non-conflicting
through traffic 1 and 2 are grouped in the second phase.
 However, in the first phase flow 7 and 8 offer
some conflicts and are called permitted right turns. Needless
to say that such phasing is possible only if the turning
movements are relatively low.
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17. Two phase signal
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18. METHODOLOGY
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19. WEBSTER METHOD
1. A proper intersection must be selected.
2. The length of the green time for approach is
calculated.
3. The minimum green time for each approach is
calculated which mainly depends on the crossing
time of the pedestrians.
4. The saturation flow rate (s) for each approach at
the intersection is measured.
5. The design flow or normal flow (q) for each
approach is determined.
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20. 6. The critical movements or lanes is to be found out and then critical
flow ratio (Y) is calculated.
Normal flow on the approach road / saturation flow on the
approach road
7. The optimum signal cycle (C0) determined by Webster method is
C0=(1.5L+5) / 1-Y
L= 2n+R
n= number of phase
R= all red time
8. Finally, the intersection capacity approaches is calculated and the
cycle time scheme is adjusted.
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21. PASENGER CAR UNIT
• Passenger Car Unit (PCU) is a metric used in Transportation
Engineering, to assess traffic-flow rate on a highway. A
Passenger Car Unit is a measure of the impact that a mode of
transport has on traffic variables (such as headway, speed,
density) compared to a single standard passenger car. This is
also known as passenger car equivalent.
• We generally express traffic flow in terms of PCU/hr in mixed
traffic conditions
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22. • PASSENGER CAR UNITS FOR DIFFERENT
VEHICLES
VEHICLES PCU VALUES
CAR,TAXI,PICKUP 1
MOTOR CYCLE 0.5
BICYCLE 0.2
HORSE DRAWN 4
BUS,TRUCK, TRACTOR 3.5
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23. DATA COLLECTION AT S.R. NAGAR
COMMUNITY HALL
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24. continued
 SR Nagar community hall Junction is an intersection of two roads
1 SR Nagar Road
2 B.K Guda Road
 Both roads carry significant vehicular traffic emerging from the
residential streets near by as well as through traffic from Balkampet
road resulting in continuous traffic jams during peak hours
 Hence putting up a traffic signal will serve the purpose of safe and
efficient movement of traffic without much vehicular delay
 Traffic flow data is collected at our selected intersection for every
15 minutes interval for a period of 8hours on both the roads.
 The normal flow and saturated flow values for each hour is
calculated by converting traffic volume counts in to PCU by using
respective PCU value as mentioned by IRC
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25. NORMAL FLOW AND SATURATED
FLOW
• For S.R. Nagar Road
Time Normal flow Saturation flow
10:00am-11:00am 1897.2 PCU/hr 7589.2 PCU/hr
11:00am-12:00pm 2238.4 PCU/hr 4326.5 PCU/hr
12:00pm-1:00pm 2126 PCU/hr 4334.5 PCU/hr
1:00pm-2:00pm 1775 PCU/hr 7106.6 PCU/hr
2:00pm-3:00pm 2032.5 PCU/hr 8130 PCU/hr
3:00pm-4:00pm 2189.2 PCU/hr 8756.9 PCU/hr
4:00pm-5:00pm 2201.9 PCU/hr 8807.6 PCU/hr
5:00pm-6:00pm 2254.7 PCU/hr 9018.8 PCU/hr
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26. • Road width =4.38 M
• Normal flow = 16714.7 PCU
• Average normal flow = 2089.33
• Average saturation flow= 8375.18
ya = qa/sa = 2089.33/8375.18= 0.24
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27. • For B.K. Guda & Street no 6 road
Time Normal flow SATURATION FLOW
10:00 am- 11:00 am 1673.7 PCU 6838.8 PCU
11:00am – 12:00pm 1937.2 PCU 7976.1 PCU
12:00pm-1:00pm 1726.8 PCU 6906.1 PCU
1:00pm-2:00pm 1947.2 PCU 7790.4 PCU
2:00pm-3:00pm 1431.1 PCU 5711.2 PCU
3:00pm-4:00pm 1556 PCU 5984 PCU
4:00pm-5:00pm 1715.8 PCU 6862 PCU
5:00pm-6:00pm 1731.8 PCU 6723.7 PCU
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28. • Road width = 5.43 m
• Average normal flow = 1714.88 PCU/hr
• Average saturation flow = 6849.13 PCU/hr
• Yb = qb/sb = 1714.88/6849.13 = 0.25
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29. CRITICAL FLOW RATIO (Y):
Y= ya + yb= 0.24+0.25 = 0.49
TOTAL LOST TIME (L):
L= 2n+R = 2* 2 +10=14 sec
R = 10 sec (assume)
OPTIMUM CYCLE LENGTH
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30. • CALCULATION OF GREEN TIME:
• Road A:
• Road B:
• Considering all pedestrian time = 10 seconds, Amber time
= 2 seconds for each phase i.e 4 seconds for two phases.
• Total Cycle length = 20+19+10+4 = 53 seconds.
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31. • SIGNAL PHASE DIAGRAMS
Signal Phase Diagram for Road A
Signal Phase Diagram for Road B
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32. CLASSIFIED VOLUME COUNT
• For S.R. Nagar road
59%
0%
25%
3% 13%
1
2
3
4
5
59 % of Motor cycles
0.97 % of Bicycles
25 % of Cars
3% of Busses
13 % of Auto Rickshaws
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33. 70%
0%
15%
4%
11%
1
2
3
4
5
70 % Of Motor Cycles
0.86% of Bicycles
15% of cars
4 % Busses, Truck, Lorry
11% of Auto Rickshaws
For B.K.Guda & Street No 6 Road
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34. RESULTS AND CONCLUSIONS
Based on the traffic data collected and calculations carried out the
following results are obtained
• The Signal Cycle Length is 53 seconds.
• The optimum cycle time is 50.98 seconds.
• The peak hour volume flow is 2254.7 PCU for S.R. Nagar
road and 1947.2 PCU for B.K. Guda & Street No 6 road.
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35. • The peak periods are 5:00pm-6:00pm for S.R. Nagar road &
1:00pm-2:00pm for B.K. Guda & Street No 6 road.
• By Webster method we allocate green time of 20 seconds
for S.R. Nagar road and 19 seconds for B.K. Guda &Street
No 6 road.
• As per the classified volume count Two-wheelers are more
in both roads.
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36. • Thus, by providing signals, there will be
reduction in the conflicts. And also there will
be an orderly movement of traffic in the cross-
section for the roads of S.R. Nagar Main Road
to Vengal Rao Nagar, B.K. Guda Road and
Street No 6. As well, there is no necessary of
traffic police to regulate the traffic at Sanjeeva
Reddy Nagar Community Hall Cross Roads.
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37. REFFERENCES
• Highway Engineering- S. K. Khanna & C. E. G Justo,
Nemchand & Bros., 7th Edition.
• Traffic Engineering & Transportation Planning- L.K
Kadiyali- Khanna Publications.
• IRC Code: IRC: 93-1985.
• Ministry Of Road Transport and Highways (MORTH).
• Historical signals-signalfan.com
• The history and Evolution of Traffic Lights- Science ABC
• Design principles of traffic signal – nptel
• Robert B. Noland “ Designing Traffic Signals To
Accommodate Pedestrian Travel “ Transportation Research
Board’s Record No 1553, Traffic Control Devices , Visibility
And Evaluations, Published In 1996.
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38. • Michael et. al “Design And Development Of An Improved Traffic
Light Control System Using Hybrid Lighting System” Journal Of
Traffic & Transportation Engineering Periodical Office, Chang’an
University, 2016.
• Meftah Hrairi Et Al “Design and Development Of Sensor Based
Traffic Light System” American Journal Of Applied Xciences3 (3):
1745-1749, Published In 2016.
• N. Venkata Hussian Reddy “Signal Design For T-Intersection By
Using Webster's Method In Nandyal Town, Kurnool District Of
Andhra Pradesh” An M.Tech Thesis, International Research Journal
Of Engineering And Techonology (IRJET) Published In 2016.
• Yao Wu Et Al “Development of an Optimization Traffic Signal
Cycle Length Model For Signalized Intersections In China”
Mathematical Problems In Engineering Volume 2015 (2015), Article
Id 954295.
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39. 4/6/2022 39