Rumble strips (also known as sleeper lines or alert strips) 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 that engineers consider during design. Other names Rumble strips are also known as audible lines, sleepy bumps, wake up calls, growlers, drift lines, waker-uppers and drunk bumps. Placement 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. Portable rumble strips, also called Andreas strips, can be used to alert traffic to upcoming lane closures or road works to prevent collision with signage and barriers. 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. Types There are several different ways to install rumble strips: Rolled-in, applied to newly laid asphalt pavement while it is still warm and moldable. Milled-in, applied to existing hardened asphalt or concrete roads. Formed, a corrugated form is pressed into fresh concrete. Raised plastic or ceramic units, fastened to asphalt or concrete pavement and often with a reflector built into the edge. Botts' dots are a common installation. Profiled thermoplastic