August 18


How to Get the Most Out of Congested Freeways

By Mike Spack

August 18, 2015

active traffic management systems, atms, freeway, traffic, traffic congestion, Traffic Control

Randy McCourt from DKS Associates gave an interesting talk about Active Traffic Management Systems (Jargon Alert:  ATMS) at the 2015 ITE Western District annual meeting. Basically, ATMS is using technology to provide information and better meter traffic along congested corridors to eek out better traffic operations.  You can read Randy’s paper here.

Key statistics related to ATMS based on the four federally funded pilot projects (including one along I-35W in Minneapolis, MN):

Speed & Volume Relationship

  • Costs range between $250,000 and $600,000 per lane mile
  • Decreased rear-end crashes 5-10%
  • Improved speed, travel times, and volumes carried by 7-12%
  • Improved corridor reliability by more than 13%

Traffic engineers are taught the basic relationship between flow and speed that’s shown on the right.  There’s a tipping point around 2,000 vehicles per hour per lane when speed greatly decreases and throughput greatly diminishes.  This is when we see stop and go traffic on freeways.  Applying ATMS strategies tries to get traffic moving at a speed/flow closer to the tipping point without going over the tipping point.

ATMS Operational Strategies:

  • Adaptive Ramp MeteringWashington State DOT
  • Adaptive Traffic Signal Control
  • Advanced Traveler Information
  • Dynamic Advisory Speed
  • Dynamic Junction Control
  • Dynamic Contraflow
  • Dynamic Lane Use Control
  • Dynamic Merge Control
  • Dynamic Shoulder Use
  • End of Queue Warning
  • Transit Signal Priority

Learn more at FHWA’s Site about Active Traffic Management.

Photo Sources:  Washington State DOT and Randy McCourt’s paper

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Mike Spack

My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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