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







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Neighborhood Traffic Operations: Arterial Traffic Calming Program

Traffic calming on arterial streets is challenging because of the multiple purposes served by arterial streets.  Arterial streets move people and goods efficiently within and through the City, provide routes for quick and efficient emergency response; and serve as your neighborhood street.

Calming traffic  encompasses a broad range of measures used to design and operate streets to improve safety, and encourage the traveling public to drive more slowly.  Narrow streets, curved streets, trees, and parked cars can send visual cues to the  driver to travel at slower speeds.  Our staff works proactively with other programs within Seattle Department of Transportation (SDOT) and other Departments to design and construct roads that encourage drivers to drive the designated speed limit.

Although the Arterial Traffic Calming (ATC) Program applies a wide range of measures to arterial streets, the primary tools include speed cushions and radar speed signs.  Click on Arterial Traffic Calming Map to see where arterial traffic calming devices have been installed around the City.

Step 1 - Community Request

An individual or group can request traffic calming for an arterial street by calling SDOT Neighborhood Traffic Operations at (206) 684-0353. If you are leaving a message please include your name, address, a phone number, e-mail address, and the intersection. You may also email us at

SDOT will respond to your request within weeks. Sometimes there is not a speed study for the corridor or the speed study is out of date. If this is the case, a 7-day speed survey may be conducted. Residents are always welcome to call SPD directly at 206-684-8722 to request additional enforcement. Please specify the street you are concerned about and the cross street. It is also helpful to specify the time of day you believe has the most speeders.

Once SDOT verifies there is a speeding concern, your street will be placed on the Arterial Traffic Calming (ATC) list for further review.

Step 2 Preliminary Traffic Safety Analysis and Prioritization

In the winter, SDOT will prioritize the ATC list. 

Staff will review the streets with the highest speeds and prioritize them by taking into consideration the pedestrian master plan, the bicycle master plan, and collision history.

Approximately 30 streets will be prioritized for radar speed trailer deployment.  The radar speed trailer detects and displays the speed of oncoming vehicles.  The radar speed trailer reminds drivers to drive responsibly.  The radar speed trailer is only on the street for a few days.  SDOT staff can use the data gathered by the trailer to determine if additional measures are necessary.

Step 3 – Arterial Traffic Calming Implementation

Based on funding, streets will be prioritized for Physical Traffic Calming Devices. These devices are usually permanently installed radar speed display signs or  speed cushions, but other devices are also considered based on the street’s design characteristics and available funding.

If your street has excessive speed (15% of the drivers are driving 5 miles or more over the speed limit, but does not qualify for ATC funds, you may be directed to Other Funding Sources.

If there is a school located on the arterial street you are concerned about, please contact  Particularly if there is school crosswalk, flashing beacons with a 20 mile an hour when children are present a sign may be an option.

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