Reflective studs used to mark the limits of
traffic lanes, invented by Percy Shaw
(1890-1976) in England, as a road safety
device in 1934. A cat's-eye stud has two
pairs of reflective prisms (the eyes) set in
a rubber pad, which reflect the light of a
vehicle's headlamps back to the driver. When
a vehicle goes over a stud, it moves down
inside an outer rubber case; the surfaces of
the prisms brush against the rubber and are
thereby cleaned.