There's another variant here in Australia (and NZ, and I'm sure in other places too), which is a set of raised paint lines on the road which will give you a rumbling sound as you drive over them. The same technique is used in transition areas from high to low speed (like a highway exit) or where two lanes of high-speed traffic will be merging, that kinda thing where you want people to be awake.
A sample can be seen here, clearly showing the raised paint goop.
They're called, logically enough, 'audible lines', and are best defined as:
...a line on a road that is made up of a series of closely spaced raised pieces of material designed to create a continuous noise or vibration if driven on by a motor vehicle
(Reg 323A, New South Wales Road Rules 2008)