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
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