Longitudinal rumble strips are milled or raised elements on the pavement intended to alert inattentive drivers through vibration and sound that their vehicles have left the travel lane. There are a number of possible applications that can be used: Shoulder rumble strips are installed on a shoulder near the edge of the travel lane. They significantly reduce run-off-road (ROR) crashes. Edge line rumble strips are very similar to shoulder rumble strips, but placed at the edge of the travel lane, typically in line with the edge line pavement marking. Center line rumble strips are installed at or near the center line of an undivided roadway, and may be comprised of either a single or double line of rumbles. They reduce cross center line crashes such as head-on collisions and some run-off-road left crashes. Rumble stripes are either edge line or center line rumble strips where the pavement marking is placed over the rumble strip. This countermeasure increases nighttime visibility of the pavement marking.