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By: Richard Holt, P.E.
Have you ever wondered what that terrible noise and vibration is when you slightly veer over the center or edge line of the roadway?
Those noisy bumps are referred to as rumble strips or rumble stripes. They are formed when a strip of asphalt has been milled (cut) or rolled with a special tool. They are meant to produce sound and vibration to alert drivers when they cross over the centerline or edge line of the roadway. By alerting the driver rumble strips reduce head-on and roadway departure crashes.
Head-on crashes represent approximately 12 percent of all fatal crashes, and approximately 60 percent of all fatal crashes are roadway departure related. Where centerline rumble strips have been installed on rural two-lane roadways, head on and opposite direction side swipe crashes have been reduced by 38 – 50%. Rumble strips on the shoulder of a rural two-lane roadway can reduce roadway departure crashes by 26-46%.
Benefits of rumble strips include:
- Reduction in run off the road crashes caused by driver inattention, driver error, poor visibility and fatigue
- Inexpensive to install
- Little to no maintenance
- Ability to install on new or existing pavements
- Inconvenience for cyclists
- Excessive noise for nearby residents
- Potential for pavement degradation
State agencies have acknowledged the inconvenience for cyclists. To minimize the inconvenience, “bicycle gaps” in the edge line rumble strip are often provided to give riders a periodic smooth surface to move between the travel lane and the shoulder should it become necessary. Bicycle gaps are typically 15’ long between 60’ long sections of rumble strips.
Sain Associates has been a part of numerous roadway safety assessment teams across Alabama and Tennessee where rumble strips are incorporated into our safety improvement recommendations.
Rumble strips may be annoying, but they have been proven to save lives.
For more information, check out this information from FHWA: