Why This Reflector Wants To Be Run Over

The classic cat's eye road stud is built to be run over, and that's how it stays clean. A tyre pushes its rubber block down into a cast-iron pot under the road, and on the way down the glass lenses slide past rubber wipers fixed in the pot (the classic design even holds rainwater in its base to wet them). The wheel rolls on, the block springs back, and the clean glass shines back at the next car's headlights. Road grime is the main thing that dims road reflectors: in one Texas field test, raised markers lost about half their brightness within a month, mostly to dirt. Many modern road studs are rigid and don't clean themselves; this is the traditional British cat's eye. Sources: Percy Shaw, patent GB457536A · road-stud patent WO2007135375A1 · US4088416A (the traditional Catseye's construction) · Ullman, "Retroreflective Raised Pavement Marker Field Testing", Texas Transportation Institute report 1946-1 (1992) #engineering #roads #driving #howitworks