Rumble strips are grooves or rows of raised pavement markers placed perpendicular to the direction of travel to alert inattentive drivers. a vehicle passes over the rumble strips, noise and vibration are produced, alerting the driver they are approaching a hazard.
The Washington State Department of Transportation (WSDOT) currently uses Roadway Rumble Strips and Shoulder Rumble Strips (SRS) as a matter of policy. We are also experimenting with Centerline Rumble Strips in a few locations.
Roadway rumble strips are placed across the traveled way to alert drivers approaching a change of roadway condition or a hazard that requires substantial speed reduction or other maneuvering.
Shoulder rumble strips are placed on the shoulders just beyond the traveled way to warn drivers they are entering a part of the roadway not intended for routine traffic use. WSDOT uses milled-in SRS as their standard design.
Centerline Rumble Strips are placed on centerline of undivided highways to warn drivers they are leaving their intended lane of travel