Current Practices in Traffic Signal Coordination

Current Practices in Traffic Signal Coordination Presented by:

Wayne Kurfees*Kimley-Horn and Associates, Inc.* PE in AZ, IA, NC, TN, and TX

Workshop on Best Practices for Signal Timing and OperationsJanuary 9, 2005

Presented by:

Wayne Kurfees*Kimley-Horn and Associates, Inc.* PE in AZ, IA, NC, TN, and TX

Workshop on Best Practices for Signal Timing and OperationsJanuary 9, 2005 Kimley-Horn

and Associates, Inc.

Kimley-Hornand Associates, Inc.

DisclaimerDisclaimer

This presentation is based on current traffic signal coordination practices in the Dallas-Fort Worth Metroplex and may or may not reflect the state of the practice in other areas

This presentation is based on current traffic signal coordination practices in the Dallas-Fort Worth Metroplex and may or may not reflect the state of the practice in other areas

Kimley-Hornand Associates, Inc.

Wayne’s RulesWayne’s Rules

The motorists are the ultimate judges of the success of a signal timing project

Before developing the new timing, be sure to understand the timing strategy that’s currently in effect

The motorists are the ultimate judges of the success of a signal timing project

Before developing the new timing, be sure to understand the timing strategy that’s currently in effect

Kimley-Hornand Associates, Inc.

General PhilosophiesGeneral Philosophies

Progression-based solutions• Continuous green bands if possible,

with appropriate consideration of the volumes turning onto and off of the arterial

• Otherwise, limit the number of stops for through traffic on the arterial

Progression-based solutions• Continuous green bands if possible,

with appropriate consideration of the volumes turning onto and off of the arterial

• Otherwise, limit the number of stops for through traffic on the arterial

Kimley-Hornand Associates, Inc.

General Philosophies, cont. General Philosophies, cont.

Optimize the phase sequence to achieve two-way progression

Optimize the phase sequence to achieve two-way progression

Kimley-Hornand Associates, Inc.

With One-way Progression

NB

NB

Kimley-Hornand Associates, Inc.

With Two-way Progression

NB

NB

SB

SB

Kimley-Hornand Associates, Inc.

General Philosophies, cont.General Philosophies, cont.

When timing a grid of arterials, try to attain interlocking (i.e. both north-south and east-west) progression

When timing a grid of arterials, try to attain interlocking (i.e. both north-south and east-west) progression

Kimley-Hornand Associates, Inc.

Plano

Richardson

Garland

Carrollton

Dallas

Farmers Branch

Addison

Kimley-Hornand Associates, Inc.

General Philosophies, cont.General Philosophies, cont.

Whenever possible, provide seamless progression across jurisdictional boundaries

Whenever possible, provide seamless progression across jurisdictional boundaries

Kimley-Hornand Associates, Inc.

Plano

Richardson

Garland

Carrollton

Dallas

Addison

Farmers Branch

Kimley-Hornand Associates, Inc.

Plano

Richardson

Garland

Carrollton

Dallas

Farmers Branch

Addison

Kimley-Hornand Associates, Inc.

Plano

Richardson

Garland

Carrollton

Dallas

Addison

Farmers Branch

Kimley-Hornand Associates, Inc.

Plano

Richardson

Carrollton

Dallas

Farmers Branch

AddisonGarland

Kimley-Hornand Associates, Inc.

Plano

RichardsonGarland

Carrollton

Dallas

Farmers Branch

Addison

Kimley-Hornand Associates, Inc.

Plano

Richardson

Garland

Carrollton

Dallas

Farmers Branch

Addison

Kimley-Hornand Associates, Inc.

General Philosophies, cont.General Philosophies, cont.

Minimize the number of control groups

Minimize the number of control groups

140”

130”

96”

92”

Kimley-Hornand Associates, Inc.

“Before” Cycle Lengths (PM Peak):144 seconds 160 seconds 80 seconds

Frankford

Trinity Mills

PGBT

Marsh Midw

ay

DN TDN T

N

DallasDallas

CarrolltonCarrollton

Kimley-Hornand Associates, Inc.

“After” Cycle Lengths (PM Peak): 160 seconds 80 seconds

Frankford

Trinity Mills

PGBT

Marsh Midw

ay

DN TDN T

N

DallasDallas

CarrolltonCarrollton

Kimley-Hornand Associates, Inc.

“After” Cycle Lengths (PM Peak): 160 seconds 80 seconds

Frankford

Trinity Mills

PGBT

Marsh Midw

ay

DN TDN T

N

DallasDallas

CarrolltonCarrollton

Kimley-Hornand Associates, Inc.

Richardson

Garland

Dallas

Kimley-Hornand Associates, Inc.

Understand the Client’s Preferences and LimitationsUnderstand the Client’s Preferences and Limitations Minimum split times

• Coordinated phases

• Other through phases

• Left-turn phases

Signal sequences• Are lead-lag sequences allowed?

• Is it okay to use “Dallas” phasing (or similar techniques) to avoid the yellow trap if the leading side has protected-permissive left turns?

• Is it okay for the sequence to change as a function of the timing plan?

Minimum split times• Coordinated phases

• Other through phases

• Left-turn phases

Signal sequences• Are lead-lag sequences allowed?

• Is it okay to use “Dallas” phasing (or similar techniques) to avoid the yellow trap if the leading side has protected-permissive left turns?

• Is it okay for the sequence to change as a function of the timing plan?

Kimley-Hornand Associates, Inc.

Understand Any Special Requirements and Limitations of the Particular Brand of System (or Controller Type)

Understand Any Special Requirements and Limitations of the Particular Brand of System (or Controller Type)

Offset reference points Are splits in seconds or percent? Controller-specific limitations

• Example: With at least one controller brand, you must add 1 second to the calculated minimum split times

Offset reference points Are splits in seconds or percent? Controller-specific limitations

• Example: With at least one controller brand, you must add 1 second to the calculated minimum split times

Kimley-Hornand Associates, Inc.

Motorist ConsiderationsMotorist Considerations Are the progression speeds realistic?

• What if the actual platoon speeds are greater than the posted speed limit?

Whenever a major flow has to stop…• A short stop is better than a long one

• Try not to have the stop occur at an insignificant minor street

• For safety’s sake, the platoon should arrive on red (rather than encounter an unexpected yellow)

Are the progression speeds realistic?• What if the actual platoon speeds are

greater than the posted speed limit? Whenever a major flow has to stop…

• A short stop is better than a long one

• Try not to have the stop occur at an insignificant minor street

• For safety’s sake, the platoon should arrive on red (rather than encounter an unexpected yellow)

Kimley-Hornand Associates, Inc.

Pedestrian ConsiderationsPedestrian Considerations Some locations require full

accommodation of the pedestrian intervals• CBD intersections (and other locations

with significant pedestrian volumes)• School crossings (at least during the

crossing times)• Coordinated phases• Pretimed intersections• Other locations without push buttons

(if “where pedestrian movements regularly occur”)

Some locations require full accommodation of the pedestrian intervals• CBD intersections (and other locations

with significant pedestrian volumes)• School crossings (at least during the

crossing times)• Coordinated phases• Pretimed intersections• Other locations without push buttons

(if “where pedestrian movements regularly occur”)

Kimley-Hornand Associates, Inc.

Pedestrian Considerations, cont.Pedestrian Considerations, cont. Otherwise, the minor-phase split will

generally not accommodate the walk and ped clear intervals (and a resynchronization will have to occur after the ped call is served)

Otherwise, the minor-phase split will generally not accommodate the walk and ped clear intervals (and a resynchronization will have to occur after the ped call is served)

Kimley-Hornand Associates, Inc.

Use of the Optimization ModelUse of the Optimization Model Understand the model’s strengths

and weaknesses Make adjustments as needed to

overcome the weaknesses Use the model as a tool but

generally not as the final result

Understand the model’s strengths and weaknesses

Make adjustments as needed to overcome the weaknesses

Use the model as a tool but generally not as the final result

Kimley-Hornand Associates, Inc.

Timing Plan DevelopmentTiming Plan Development Build and calibrate the model

• Does it reflect what was observed on the street?

• Are progression speeds realistic? Use a “master” intersection Make the best use of the model’s

optimization• Make adjustments as appropriate

Build and calibrate the model• Does it reflect what was observed on

the street?

• Are progression speeds realistic? Use a “master” intersection Make the best use of the model’s

optimization• Make adjustments as appropriate

Kimley-Hornand Associates, Inc.

Timing Plan Development, cont.Timing Plan Development, cont. “On-screen” fine-tuning

• Eliminate excess time for minor phases

• Adjust non-critical phase times to provide the best re-start (i.e. try to avoid the need for multiple stops before “getting back into the band”

• Try to make more “good things” happen

“On-screen” fine-tuning• Eliminate excess time for minor

phases

• Adjust non-critical phase times to provide the best re-start (i.e. try to avoid the need for multiple stops before “getting back into the band”

• Try to make more “good things” happen

Kimley-Hornand Associates, Inc.

Timing Plan Development, cont.Timing Plan Development, cont. Prior to beginning the

implementation, review the proposed timing with the client “on-screen”

Prior to beginning the implementation, review the proposed timing with the client “on-screen”

Kimley-Hornand Associates, Inc.

Timing Plan ImplementationTiming Plan Implementation

Prepare final timing in the appropriate format

Make maximum practical use of automated interfaces between the optimization program and the signal system’s database

Double-check the database before the new timing plans actually operate on the street

Prepare final timing in the appropriate format

Make maximum practical use of automated interfaces between the optimization program and the signal system’s database

Double-check the database before the new timing plans actually operate on the street

Kimley-Hornand Associates, Inc.

On-street Fine-tuningOn-street Fine-tuning

Make the plans “drive” as smoothly as possible for the majority of the motorists

Generally, make use of iterative, small adjustments

Encourage the client’s participation

Make the plans “drive” as smoothly as possible for the majority of the motorists

Generally, make use of iterative, small adjustments

Encourage the client’s participation

Kimley-Hornand Associates, Inc.

SummarySummary

Good signal timing involves both art and science

Make wise use of the models… but don’t be afraid to use good judgment to improve the on-street result

Good signal timing involves both art and science

Make wise use of the models… but don’t be afraid to use good judgment to improve the on-street result