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Rumble strips are a low-cost measure used to address one of the most serious types of traffic crashes: a lane departure crash. They consist of a set of transverse grooves applied on the shoulder or centerline of a roadway.
Rumble strips provide a tactile and audible warning to alert inattentive (distracted, drowsy, unfocused, etc.) drivers who may unintentionally drift out of their lane. This warning gives the driver an opportunity to correct their action or reduce speed, which may help them avoid or reduce the severity of a crash.
Shoulder rumble strips have been in use all over the country for many years and their safety benefits are well-documented, but over the years Michigan has been leading the way for centerline rumble strips. Between 2008 and 2010, MDOT undertook the largest initiative of its kind to install 5,400 miles of centerline rumble strips (and an additional 1,700 miles of shoulder rumble strips) on high-speed rural highways across the state. This system-wide installation provided a unique opportunity to evaluate the effectiveness of non-freeway rumble strips, which was done through a two-phase research project.
Safety by the numbers
A before-and-after crash study performed for the 2008-2010 installation locations found significant reductions across all crash severities and lane departure crash types, including:
- 50 percent reduction in head-on crashes,
- 46 percent reduction in run-off-the-road crashes,
- 51 percent reduction in fatal crashes, and
- 41 percent reduction in incapacitating injury crashes.
Rumble strips have become a safety standard and will continue to save lives on Michigan's roads.