The state’s electronic traffic information system is made up of many parts.
Traffic-counting loops consist of low-voltage wire coils buried in the roadway. Each one sends an electrical pulse when a vehicle passes over it.
The transportation department’s Seattle-area traffic information
webpage, which covers the region from Smokey Point to the Pierce County line, color-codes roads based on the level of congestion. Green is wide open, yellow is moderate traffic, red is heavy and black is stop and go. This data comes from the loops.
Hundreds of traffic information cameras are mounted alongside interstate freeways and state highways. They are connected to the state’s Traffic Management Center in Shoreline, a large, C-shaped room equipped with more than 40 monitors. There, transportation department staff can see what’s going on from the Stillaguamish River to the King-Pierce County line. Six other centers are located around the state.
Generally, the monitors receive feeds from cameras at key locations with frequent heavy traffic. The center is occupied 24 hours, seven days a week by at least a couple of staff members.
When a call about a highway incident is placed to 911, the information is relayed to the center. Then staff can look at the incident with the nearest camera to see if the reported location is accurate — often, it’s not — and to assess traffic conditions, said Bronlea Mishler, a spokeswoman for the state Department of Transportation.
Staff can maneuver many of the cameras from the center with a keyboard or a joystick to look at the roadway from different directions.
Then the incident is posted on the traffic webpage and on the 511 public information phone line. Tweets go out and notices are sent to the media. One of the transportation department’s Incident Response teams, which help clear roads and help drivers at accident scenes, may also be sent out.
Other parts of the state’s traffic information system include electronic message boards, located in the more congested areas; highway advisory radios, which send low-frequency broadcasts from roadside transmitters about local road conditions; mini-weather stations that report information to a webpage; and ramp meters, which are controlled from the traffic center.