Measuring Neighborhood Traffic Safety Benefits by Using Real-Time Driver Feedback Technology

Abstract

Local jurisdictions frequently respond to public concerns about speeding on neighborhood streets. When a speed study confirms that a significant percentage of vehicles are exceeding the posted speed limit, a traffic engineer carefully reviews the conditions to determine if additional safety measures need to be implemented. Preserving roadway safety for the motorized and the nonmotorized public alike who share the roadway is essential. Each jurisdiction is likely to use any number of solutions from its traffic safety toolbox. Additional signing, mobile radar speed display units, neighborhood speed watch programs, or targeted police enforcement may help discourage drivers from traveling at unacceptable speeds. Physical devices, such as traffic circles, speed humps, and chicanes, can also be considered but will affect emergency vehicles by increasing their response times. To balance increased driver awareness of travel speeds with vehicle accessibility, the King County Department of Transportation in Washington State installed four radar speed signs along 108th Avenue NE between NE 124th Street and Juanita-Woodinville Way NE. These radar speed signs, installed directly below the black-and-white regulatory speed limit signs, alerted each driver by indicating travel speed. To evaluate the effectiveness of these signs, speed studies were conducted before, during, and after installation. The results from these studies are presented, installation and maintenance of this device are discussed, and conclusions are drawn about whether these signs have been successful in calming neighborhood traffic.