Performance Analysis of Centerline and Shoulder Rumble Strips Installed in Combination in Washington State

Washington State Department of Transportation (WSDOT) began installing rumble strips on undivided highways in 1999 as a countermeasure for roadway departure crashes. Installations on the shoulders were intended to reduce run-off-the-road crashes, while centerline rumble strips targeted reductions in cross-centerline crashes. A March 2011 report detailed the performance of centerline rumble strips on Washington State highways. This present study: 1) examines the combined effects of centerline and shoulder rumble strips; 2) details the performance of rumble strips on undivided highways in Washington State under a variety of conditions; 3) explores various traffic volumes, geometric conditions, lane and shoulder widths, and driver contributing circumstances; and 4) compares various installation scenarios with shoulder and centerline rumble strip installation at different times, as well as simultaneous installation.