Rumble Strips
Rumble strips are small indentations or narrow raised strips on
the highway or shoulder. They are put there to vibrate the steering
wheel and to make a noise inside the vehicle to get the attention of
the driver. Here are the reasons rumble strips are placed where
they are:
λ
To alert the driver to a decision point ahead - such as an
intersection after a long stretch of uninterrupted road.
λ
To wake the driver who may have dozed off - used on the
shoulder of the road, usually along a long straight-away.
λ
To caution the driver about the danger of passing - used in the
center of some two-lane roads where passing is hazardous.
λ
To alert the driver to some new or unexpected situation ahead -
such as dangerous curves, a toll booth, a railroad crossing, or the
end of a freeway.
http://safety.fhwa.dot.gov/ped_bike/docs/ryr.pdf