status report on traffic signal optimization in the washington region
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Item #12. Status Report on Traffic Signal Optimization in the Washington Region. Edward D. Jones Prince George’s County DPW&T and Chair, Traffic Signals Subcommittee Transportation Planning Board March 18, 2009. Background.

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status report on traffic signal optimization in the washington region

Item #12

Status Report onTraffic Signal Optimizationin the Washington Region

Edward D. Jones

Prince George’s County DPW&T

and Chair, Traffic Signals Subcommittee

Transportation Planning Board

March 18, 2009

background
Background
  • TPB requested a regional traffic signal optimization status report at the January 28 meeting
    • Identified as CLRP priority area
  • Follows from the 2002-2005 signal optimization Transportation Emissions Reduction Measure (TERM)
what does it mean for signals to be optimized
What Does It Mean for Signals to Be Optimized?
  • Traffic signals re-timed for optimal performance, considering
    • traffic loads
    • cross traffic, left and right turns
    • pedestrians
  • Coordination of multiple signals (e.g., downtown areas, corridors)
optimized does not always mean minimal delay for an individual motorist
Optimized Does Not Always Mean Minimal Delay for an Individual Motorist
  • If there are high traffic volumes / left and right turns / high cross-traffic volumes
  • If you are traveling in the opposite direction of predominant flow
  • Ensuring the safety of and sufficient crossing time for pedestrians
how do we know that signals are optimized
How Do We Know that Signals are Optimized?
  • Engineers do not rely solely on the “raw” computer output
  • Before and after field observations help verify that the optimization process has been successful
  • Ongoing field observations and monitoring from the traffic control center are important, with fine-tuning if necessary
  • These monitoring and spot checks activities, as well as responding to citizen inquiries and complaints, all help ensure the system remains working properly
survey
Survey
  • TPB staff surveyed transportation agencies by email February and March 2009
  • Survey focused on whether signals were optimized or checked within calendar years 2006-2008
    • Follows the 3-year engineering rule-of-thumb
  • Responses reflect >98% of all signals in the region that are subject to optimization
    • Signals not subject to optimization were not included in the survey (e.g., firehouse emergency signals and pedestrian crosswalk flashers)
optimization results 2006 2008
Optimization Results (2006-2008)
  • Approximate total signals in region: 5,400
  • Total optimized, checked, or adjusted: 80%
    • Computer optimized: 56%
    • Other check or adjustment: 24%
    • Weighted average (2005 TERM methodology): 68%
  • Not checked: 18%
  • No report: 2%
how is the region doing on optimization compared to 2005
How is the Region Doing on Optimization Compared to 2005?
  • Weighted average of 68% is the same as in 2005
  • However, we are doing better than that may indicate because:
    • The most critical signals in many cases are being checked and optimized even more frequently than once every 3 years
    • All agencies (with >50 signals) reported that they had optimized or checked significant numbers of their signals within the reporting period
    • Anecdotal reports of more resources annually being put into optimization – beneficial if continued
outlook
Outlook
  • Continuing awareness of and commitment to safe and effective signals operations
  • Effective interagency coordination through the Traffic Signals Subcommittee and other forums
  • The benefits of providing sufficient resources to ensure good signals operations are widely recognized
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