This document discusses signal retiming, which is the process of optimizing traffic signal timing parameters like cycle length, offset, and split times. Signal retiming can reduce delays, stops, fuel consumption, and accidents at intersections. It is conducted by collecting traffic data and analyzing it using software to determine improved signal timing plans. Signal retiming should be conducted every 1-3 years to account for changing traffic patterns and is estimated to cost $2,500 per intersection. Studies show signal retiming can reduce delays by 15-30% and lower fuel consumption and emissions.

1. SIGNAL RETIMING
BY-ALOK
KUMAR TRIPATHI
131109037
1
TRAFFIC AND TRANSPORT PLANNING
MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY ,BHOPAL

2. STRUCTURE OF THE PRESENTATION
• AIM & OBJECTIVE
• WHAT IS SIGNAL RETIMING ?
• PARAMETERS
• WHY IS SIGNAL RETIMING CONDUCTED?
• HOW IS SIGNAL RETIMING CONDUCTED?
• WHO RETIMES TRAFFIC SIGNALS?
• CONSTRAINTS OF OPTIMIZING AND OPERATING TRAFFIC SIGNALS?
• HOW OFTEN SHOULD SIGNAL RETIMING BE CONDUCTED?
• WHAT IS THE COST OF RETIMING TRAFFIC SIGNALS?
• BENEFITS OF RETIMING TRAFFIC SIGNALS
• TESTIMONIALS
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3. • AIM :- TO UNDERSTAND SIGNAL RETIMING AND ITS BENEFITS .
• OBJECTIVE :-
SIGNAL RETIMING -
WHAT
 WHY
 HOW
 WHO RETIMES
 CONSTRAINTS
 BENEFITS
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4. WHAT IS SIGNAL RETIMING ?
Signal retiming is a process that optimizes the operation of signalized inter- sections through a
variety of low-cost improvements.
This includes :-
• The development and implementation of new signal timing parameters
• Phasing sequences
• Improved control strategies
• The minimization of stops, delays, fuel consumption and air pollution emissions and the
maximization of progressive movement through a system
• Reconfiguration of a signal’s operation
• Minor roadway improvements 4

5. PARAMETERS :-
• Cycle :- the time needed to serve all phases.
• Offset :- the time from a reference point, such as the start of green or yellow of the
coordinated phase at one intersection, to the same reference point at the other intersections.
• Split :- the time allowed for each movement or phase . Their total is the cycle length.
• Progressive movement :-The offset is used to allow vehicles moving at the proper speed to
advance from intersection to intersection without stopping. This process is called progressive
movement.
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6. TERMS RELATING TO SIGNAL TIMING
Offset
Split phase
Phase 1A
Phase 1B
All signal analyses are based on through
passenger cars. This way the analyses became
portable to any sites. Then we need
conversion of other-than-passenger cars and
other-than-through vehicles. Hence we need:
• Passenger car equivalent
• (TPuCrnEi)ng movement factors
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7. TERMS RELATING TO SIGNAL TIMING
Cycle length
Phase
Interval
Change interval
All-red interval
(clearance interval)
Controller
Phase B
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8. WHY IS SIGNAL RETIMING CONDUCTED?
• Increase in traffic with the addition of new homes or stores
• Reduced delay time on the approach to an intersection
• Postpone or eliminate need for additional capacity
• Maximizes the benefits of the existing infrastructure
• Reduces aggressive driving behavior, red light running
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9. • Saves time for commercial vehicles, emergency vehicles, buses and the public
• Safety – reduce accidents by providing smoother traffic flow with fewer stops
• Accommodation of traffic flow for different times of day or days of the week
• Improved pedestrian flow, side-street movements
• Municipal cost and energy savings
• Cost effective: cost ratios of 40:1
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10. OBJECTIVES OF SIGNAL TIMING
• Reduce the average delay of all vehicles
• Reduce the probability of accidents
Minimize the possible conflict points
by assigning the right of way to
different traffic movements
Two conflicting objectives:
 More phases, less conflict
 More phases, more lost time
So, if at all possible, use:
 2 phases
 Short cycle length
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11. HOW IS SIGNAL RETIMING CONDUCTED?
• Travel time data , traffic and pedestrian volume data are
collected , to identify current operating conditions.
• A collision history and analysis are prepared. Collision
records for the past three years are obtained.
• Collected data are processed and analyzed using capacity
analysis, traffic signal timing optimization and simulation
software programs.
• Determination of improved coordination offsets using
signal coordination software programs such as SYNCHRO
,PASSER II or CORSIM (simulation software programs).
• Implementation , evaluation and final adjustments of new
timing
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12. WHO RETIMES TRAFFIC SIGNALS?
Agency responsible for the
operation of the road- ways
where signals are located.
State departments of
transportation (DOT)
Local counties and
municipalities that have
responsibility for the
operation of signals within
their jurisdictions .
Political bodies, planning
organizations and other
advisory committees.
The public is involved as
complaints and requests
often are received with
requests to update studies
or make signal timing
improvements. 12

13. CONSTRAINTS OF OPTIMIZING AND OPERATING
TRAFFIC SIGNALS?
• constraints, can be bro- ken into three general categories:
1. Institutional
2. Physical
3. Temporal
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14. Institutional constraints on signal timing optimization pertain to the allocation of
resources within an organization or agency and the relationship agencies have across
jurisdictional boundaries.
• Lack of cooperative working arrangements in multiple agencies
• Different priorities on signal control and equipment incompatibilities in separate
agencies
INSTITUTIONAL CONSTRAINTS
REASONS
SOLUTIONS
Sufficient resources (in terms of staff time and/or outsourcing contracts) should
be available. 14

15. PHYSICAL CONSTRAINTS
Physical constraints are geometric barriers to more efficient signal operation.
• Turn pockets of insufficient length, a lack of necessary turn pockets, or too few
primary lanes for servicing traffic demand (lack of capacity).
• Irregular and/or close signal spacing
• Mid-block access points may contribute enough traffic to the arterial to interfere
with progression between intersections.
REASONS
SOLUTION
In such cases, green time allocation at a signal may be used to attempt to
compensate for the limiting geometric feature(s). 15

16. TEMPORAL CONSTRAINTS
Temporal (time) constraints are related to a signal’s inability to consistently provide
adequate green time for traffic demand.
• Too much traffic for an intersection to physically process,
• Fluctuations in demand patterns
• Or when too many conflicting movements require excessive green time.
REASONS
Green time must be diverted for priority and safety reasons, regardless of
capacity conditions at an intersection. SOLUTIONS 16

17. NATIONAL
TRAFFIC
SIGNAL
REPORT CARD
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18. HOW OFTEN SHOULD SIGNAL RETIMING BE CONDUCTED?
Existing signal timing cannot operate efficiently with newer traffic patterns. Signal timing should
be fine-tuned to operate better. For traffic signals to operate efficiently, the complete retiming of
a traffic signal or system often is necessary.
• Traffic engineers should review traffic signal and system performance continuously.
• Ideally, signal timing should be reviewed every year to evaluate effectiveness and efficiency. If
necessary, a thorough signal retiming should be conducted.
• At a minimum, an operating agency should budget to retime traffic signals at least every three
years, especially in developing areas and/or areas with sustained growth.
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19. WHAT IS THE COST OF RETIMING TRAFFIC SIGNALS?
Signal retiming often is postponed or ignored due to an agency’s financial or staffing
constraints. Given the need for field data collection, data analysis, signal timing optimization,
testing and implementation, the overall signal timing process can be expensive and time
consuming. However, as discussed earlier, retiming traffic signals is necessary to maintain
efficient traffic operations.
• Estimates of the time required vary according to available expertise and equipment. On
average, it is estimated that generating four timing plans (for a.m. peak, noon peak, p.m.
peak and off-peak conditions) takes 25 to 30 hours per intersection.
• The cost of signal retiming is roughly $2,500 per intersection, including the four typical
timing plans.
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20. BENEFITS OF RETIMING TRAFFIC SIGNALS
There are three types of benefits :
DIRECT BENEFITS
SIDE BENEFITS
INDIRECT BENEFITS
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21. • The reduced delay experienced by motorists.
• Motorists experience fewer stops and reduced fuel consumption. DIRECT BENEFITS
• General public perception of reduced delay during travel.
• Reduced motorist frustration and improved safety. SIDE BENEFITS
• Minimizes diversion of traffic to local and residential neighborhoods,
potentially improving safety and traffic conditions.
• Reduced pavement wear and tear , which minimizes the maintenance
requirements of the PWD.
INDIRECT
BENEFITS 21

22. ENVIRONMENTAL BENEFIT
Reduced fuel consumption reduces emissions and, hence,
improves air quality.
Less Congestion
Improved Fuel Consumption
Vehicle Emissions Reduced
Improved Air Quality
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23. DELAY AT TRAFFIC SIGNALS
Time (years)
Delay
Do Nothing
Periodic Retiming
Constant Retiming
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24. Time (years)
Delay
“WOW!!! 30% Improvement!!!”
Do Nothing
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25. SAVINGS FROM SIGNAL RETIMING
Savings at the end of 9 years — Area A + B
A
B
C
1 2 3 4 5 6 7 8 9 10
Years
User costs
If retimed only once at the end of 3 years
Savings at the end of 6 years — Area A
If retimed at the end of 3 and 6 years
Savings at the end of 9 years — Area A + B + C
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26. TESTIMONIALS
A statewide traffic signal retiming program in
California found the following benefits:
• 7.2% reduction in travel time
• 15% reduction in delay
• 8.6% saving in fuel
• Benefit/cost ratio 58:1
An advanced traffic control retiming in Oakland County,
Michigan (a large suburban area) achieved:
• 30% reduction in delay
• 19% increase in peak hour speeds
• 6% reduction in accidents
• 33% reduction in stops
A new signal system and improved signal timing conducted
in Texas (a mid-sized urban area) achieved:
• 14% reduction in travel time
• 37% reduction in delay
• 9.1% reduction in fuel consumption
• 14.2-percent reduction in stops
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27. A traffic signal retiming program in Burlington,
Canada, found the following benefits:
• 7% savings in travel time
• 11% saving in stops
• 6% saving in fuel consumption
An advanced traffic control retiming in St. Augustine ,
USA at a 11-intersection achieved:
• 36% reduction in arterial delay
• 10% reduction in arterial travel time
• 49% reduction in arterial stops
A statewide traffic signal retiming program in Kitchener-
Waterloo, Canada found the following benefits:
• 10% reduction in travel time
• 27% reduction in delay
• 20% saving in stops
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28. REFERENCES
 ITE JOURNAL / APRIL 2004
 GOOGLE
 GOOGLE IMAGES
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THANK YOU ....... 