Rumble strip

Rumble strips, also known as sleeper lines, rumple strips, alert strips, audible lines,"the corduroy", growlers, "drift lines", "drunk bumps", and "woo woo" boards, are a road safety feature to alert inattentive drivers of potential danger, by causing a tactile vibration and audible rumbling transmitted through the wheels into the vehicle interior. A rumble strip is applied along the direction of travel following an edgeline or centerline, to alert drivers when they drift from their lane. Rumble strips may also be installed in a series across the direction of travel, to warn drivers of a stop or slowdown ahead, or of an approaching danger spot.

In favorable circumstances, rumble strips are effective (and cost-effective) at reducing accidents due to inattention. The effectiveness of shoulder rumble strips is largely dependent on a wide and stable road shoulder for a recovery, but there are several other less obvious factors to consider during design.

Rumble strips are divided into transverse rumble strips, shoulder rumble strips, and centerline rumble strips, depending on how they are used.

Transverse rumble strips are placed in the travel lanes where most if not all vehicles will cross them. They are used to alert the driver of an upcoming intersection, toll booth or similar hazard. They may cross the entire road from shoulder to shoulder, or they may only be in the wheel paths.

Shoulder and centerline rumble strips are used to reduce lane departure crashes. Centerline rumble strips are used on undivided highways to reduce cross-over incidents and resultant head-on collisions. Shoulder rumble strips are used primarily to reduce run-off-road collisions. They alert distracted or drowsy drivers that they are leaving the roadway or crossing the centerline of the road. In this application, they are narrower and outside of the wheelpaths.

There are several different ways to install rumble strips:

Surface-mount raised pavement reflectors are easily scraped off by the blade on snowplows, and thus are not practical in many locations in the United States and Canada.

Rumble strips combined with pavement markings are sometimes called rumble stripes. They may be formed with raised textured plastic pavement markers, or they may use conventional pavement marking materials sprayed onto milled rumble strips. Rumble stripes have markedly increased visibility in wet nighttime conditions, when conventional markings on flat surfaces can be difficult to see.

Rumble strips were first implemented on the Garden State Parkway in New Jersey in 1952.

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