What is King County’s procedure for evaluating speed limits?
The King County speed limit evaluation procedure was developed using criteria based on the Washington State Model Traffic Ordinance (46.04; WAC 303-308), the King County Code and the Manual on Uniform Traffic Control Devices (MUTCD). The MUTCD is a Federal Highway Administration document, which has been adopted by most public agencies and provides guidelines for traffic control devices and pavement markings.
In 2018, the King County Council adopted an update which, in Section 46.04.040 (RCW 46.61.415-1 amended) empowers the Director of the Department of Local Services to “revise speed limits on all streets and roads within this county as authorized by state law; provided, that such speed limit revisions shall not exceed ten miles per hour; provided further, that any determination of the property numerical value for a speed zone will be based upon the following engineering and traffic investigation factors:
- Road surface characteristics, shoulder conditions, grade, alignment and sight distance;
- The eighty five percentile speed and pace speed;
- Roadside development and culture, and roadside friction;
- Safe speed for curves or hazardous locations within the zone;
- Parking practices and pedestrian activity;
- Reported accident experience for a recent twelve month period.
Speed limits on segments less than 1.0 mile in length may be changed administratively if the posted speed limit of the road segment varies from posted speed limits at each end of the road segment. These situations commonly occur where a city has annexed a portion of the roadway and changed the speed limit within city limits, leaving a short segment in unincorporated King County with a higher speed limit. In such cases, the County may administratively make a speed limit change of no more than 5 mph. In these cases, no detailed review is conducted.
Once a preliminary review of the road segment is completed, public comment is solicited for a period of two to three weeks, except when an administrative change is implemented for a short segment as discussed in the paragraph above. Public comments are reviewed by the County Traffic Engineer and County Road Engineer prior to recommending the change to the Director of the Department of Local Services for approval and transmittal to the King County Council to enact into law.