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Delivering a first-rate transportation system for Seattle Scott Kubly, Director







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Speed Trailers

Tool Snapshot: Speed Trailer

  • Portable trailer that displays drivers’ speeds.


  • Provides immediate feedback.
  • Does not require officer to be present.
  • Relatively low cost.
  • Can be moved to varying locations.


  • Not a substitute for permanent action.

Portable speed trailers visually display drivers’ real-time speeds compared to the speed limit. According to the U.S. Department of Justice Speeding In Residential Areas guide (pg. 18), “Speed display boards have been shown to reduce speeds and crashes, and appear to be at least as effective as speed cameras in reducing speeds, and do so more cost-effectively.” Portable speed trailers are most effective when the trailer flashes SLOW DOWN or flashes a bright white light that mimics a photo speed camera or a blue and red light that mimics a police car when drivers are moving too fast. Some speed trailers have the capability to collect traffic count data and speed data throughout the day, which can be used to identify the most dangerous traffic times when more enforcement is needed.

Speed trailers are best used in residential areas and can be used in conjunction with neighborhood speed watch programs or other safety education programs. Speed trailers need to be placed in locations where they do not block pedestrians, bicyclists, motor vehicle traffic or other vital traffic control signs. The police should be encouraged to conduct some speed enforcement downstream from the display board to increase the effectiveness of the device and educate motorists of some of the consequences they face if caught speeding. Click here or here for additional information.

A Speed Trailer

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