Active Traffic and Demand Management

Active Traffic and Demand Management (ATDM) is a strategy used by the Washington State Department of Transportation to reduce collisions associated with congestion and blocked lanes. About 25% of traffic congestion is due to events like collisions or disabled vehicles. WSDOT launched the system on August 10, 2010. The project to use ATDM on I-5, I-90 and SR 520 cost a total of $65 million. 

ATDM Video Image

How does it work?
The system uses overhead lane signs to provide advance notice of traffic conditions:

  • Variable speed limit signs direct drivers to incrementally reduce their speeds.
  • Symbols direct drivers to change lanes when a lane is blocked.
  • Overhead message signs warn drivers of slowdowns, backups and collisions ahead.

The system decreases last second avoidance maneuvers and panic braking, which are both primary factors that contribute to collisions.

Current Active Traffic and Demand Management Corridors

  • Interstate 5: Seattle
  • Interstate 90: Between Seattle and Bellevue
  • Interstate 90: Over Snoqualmie Pass
  • State Route 520: Between Seattle and Bellevue

WSDOT is one of the first state transportation agencies to use this type of Active Traffic and Demand Management system in the United States. Considered a work in progress, analysis of existing traffic management corridors for safety and congestion relief could lead to additional locations like Joint Base Lewis McChord in Tacoma.