Shoulder rumble strips are intended to reduce run-off-the-road crashes, but their effectiveness has not been analyzed. Current department policy uses Average Daily Traffic (ADT) of 2500 and higher to determine when to install rumble strips on road sections that are being reconstructed or resurfaced, but ADT may not be the best threshold of when to install rumble strips as many run-off-the-road crashes occur on rural two-lane roads with low ADT.
On asphalt pavements, shoulder rumble strips are milled continuously, but bicyclists may prefer alternating lengths with and without rumble strips to provide space to avoid motorized traffic.
Intermittent rumble strips are molded into the edge of continuously reinforced and jointed concrete pavements, but SDDOTs current practice of spacing them forty feet apart on concrete pavements may not be optimal.
Temporary rumble strips are sometimes installed in construction work zones, but there is currently no uniform policy on their use. The profile of the temporary rumble strip has gone through many changes and is thought to be adequate, but each region uses its own judgment on installation.
Full lane width rumble strips are sometimes installed at intersections and other potentially hazardous locations, but no uniform policy on their installation exists. Each region makes its own decisions on when to install rumble strips at these locations.
When chip seals are applied the profile of the milled in rumble strip is reduced. When maintenance patches are installed the rumble strip section that is covered by the patch is not replaced.
SDDOT has not yet used centerline rumble strips, but there has been speculation that use of centerline rumble strips could reduce head-on collisions in sight-restricted areas. Areas in the Black Hills might benefit significantly from use of centerline rumble strips due to extremely high traffic that occurs during the annual motorcycle rally. One of the concerns with installing centerline rumble strips only on curves and sight-restricted areas is how to let motorcycle riders know the presence of intermittent rumble strips.
A number of other states have used rumble strips extensively and have developed policies, procedures, and measures of effectiveness. By taking advantage of their experience and identifying their best practices, SDDOT may be able to use rumble strips more consistently, extensively, and effectively.