SIGNAL RETIMING

BY-

ALOK KUMAR TRIPATHI

131109037 1

TRAFFIC AND TRANSPORT PLANNING

MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY ,BHOPAL

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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• AIM :- TO UNDERSTAND SIGNAL RETIMING AND ITS BENEFITS .

• OBJECTIVE :-

SIGNAL RETIMING -

WHAT

WHY

HOW

WHO RETIMES

CONSTRAINTS

BENEFITS3

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

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. 5

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

(PCE)• Turning movement factors

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TERMS RELATING TO SIGNAL TIMINGCycle length

Phase

Interval

Change interval

All-red interval

(clearance interval)

Controller

Phase B

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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 running8

• 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 40:19

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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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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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

CONSTRAINTS OF OPTIMIZING AND OPERATING TRAFFIC SIGNALS?

• constraints, can be bro- ken into three general categories:

1. Institutional

2. Physical

3. Temporal13

• Lack of cooperative working arrangements in multiple agencies• Different priorities on signal control and equipment incompatibilities in separate

agencies

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.

INSTITUTIONAL CONSTRAINTS

REASONS

SOLUTIONSSufficient resources (in terms of staff time and/or outsourcing contracts) should be available. 14

Physical constraints are geometric barriers to more efficient signal operation.

PHYSICAL CONSTRAINTS

• 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

SOLUTIONIn such cases, green time allocation at a signal may be used to attempt to compensate for the limiting geometric feature(s). 15

Temporal (time) constraints are related to a signal’s inability to consistently provide adequate green time for traffic demand.

TEMPORAL CONSTRAINTS

• 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

NATIONAL TRAFFIC SIGNAL REPORT CARD

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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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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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BENEFITS OF RETIMING TRAFFIC SIGNALS

There are three types of benefits :

DIRECT BENEFITS

SIDE BENEFITS

INDIRECT BENEFITS

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• 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

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Less Congestion

Improved Fuel Consumption

Vehicle Emissions Reduced

Improved Air Quality

ENVIRONMENTAL BENEFIT

Reduced fuel consumption reduces emissions and, hence, improves air quality.

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DELAY AT TRAFFIC SIGNALS

Time (years)

Del

ay

Do Nothing

Periodic Retiming

Constant Retiming

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Time (years)

Del

ay

“WOW!!! 30% Improvement!!!”

Do Nothing

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SAVINGS FROM SIGNAL RETIMING

A

B

C

1 2 3 4 5 6 7 8 9 10Years

Use

r co

sts

If retimed only once at the end of 3 years

Savings at the end of 6 years — Area ASavings at the end of 9 years — Area A + B

If retimed at the end of 3 and 6 yearsSavings at the end of 9 years — Area A + B + C

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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

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

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

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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

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

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

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REFERENCES

ITE JOURNAL / APRIL 2004

GOOGLE

GOOGLE IMAGES

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THANK YOU .......