Several experimental Japanese "melody roads" have been deployed, whose cut grooves and bumps play distinctive songs through your car, but only when you drive slowly and carefully down them. This seems like a potentially useful bit of social engineering — set the musical timing on a road at the safe speed, and combine that with timed traffic lights that reward you with a "green wave" if you stick to the limit, and you'd have a pretty good set of cues telling you how to travel at speed. Bobbie Johnson writes in the Guardian:
A team from the Hokkaido Industrial Research Institute has built a number of "melody roads", which use cars as tuning forks to play music as they travel.
The concept works by using grooves, which are cut at very specific intervals in the road surface. Just as travelling over small speed bumps or road markings can emit a rumbling tone throughout a vehicle, the melody road uses the spaces between to create different notes.
Depending on how far apart the grooves are, a car moving over them will produce a series of high or low notes, enabling cunning designers to create a distinct tune.
