Portable Radar Speed Trailers Help Address Speeding Issues

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Portable radar speed trailer in use.

Does it feel like vehicles are traveling faster than the posted speed limit along the county road outside your home? You may want to consider the use of a King County portable speed trailer to help address this issue.


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Sign Technician arrives at site with portable radar speed trailer.

Portable radar speed trailers, which detect and display the speed of oncoming vehicles, promote traffic safety by controlling speeding in a way that is informative, but not intimidating. Portable speed trailers visually display drivers’ real-time speeds compared to the speed limit. They are effective in reducing speeds and increasing awareness of local speed limits. The trailers do not take photos of vehicles or issue speeding tickets.


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Installing trailer in a safe location on the shoulder of the road.

Portable radar speed trailers are placed at select locations for five day periods: from Monday to Friday. The trailers are towed to the site by a trained technician and safely installed on the shoulder of the road, facing oncoming traffic. Once the trailer is programmed, it tracks the speed of oncoming vehicles. Vehicle speed is displayed brightly on the trailer for drivers to see. When drivers are traveling too fast, the display panel flashes a “SLOW DOWN” warning in red lettering. Trailers are battery powered and equipped with antitheft tracking devices.


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Locking trailer wheels in place.

King County has a small number of portable radar speed trailers available for dispatch on unincorporated King County roadways. If you want to schedule a radar speed trailer in your neighborhood, call our 24/7 Road Maintenance helpline at 206-477-8100 or email maint.roads@kingcounty.gov with your request. Please include your address and phone number so that we can contact you to schedule the installation.