Editing Retroreflector (section)

===On roads===
{{See also|Raised pavement marker}}
[[File:Bicycle Safety (using retroreflector and Cat-Eye showing day & night difference).gif|thumb|Retroreflector and cat-eye on a [[bicycle]]]]
[[File:CarWithReflectiveStickers.jpg|thumb|Car with reflective stickers]]
Retroreflection (sometimes called retroflection) is used on [[road]] surfaces, [[road sign]]s, [[vehicle]]s, and [[clothing]] (large parts of the surface of special [[safety clothing]], less on regular coats). When the headlights of a car illuminate a retroreflective surface, the reflected light is directed towards the car and its driver (rather than in all directions as with diffuse [[reflection (physics)|reflection]]). However, a [[pedestrian]] can see retroreflective surfaces in the dark only if there is a light source directly between them and the reflector (e.g., via a flashlight they carry) or directly behind them (e.g., via a car approaching from behind). "[[Cat's eye (road)|Cat's eyes]]" are a particular type of retroreflector embedded in the road surface and are used mostly in the UK and parts of the [[United States]].

Corner reflectors are better at sending the light back to the source over long distances, while spheres are better at sending the light to a receiver somewhat off-axis from the source, as when the light from [[headlight]]s is reflected into the driver's [[Human eye|eye]]s.

Retroreflectors can be embedded in the road (level with the road surface), or they can be raised above the road surface. [[raised pavement marker|Raised reflectors]] are visible for very long distances (typically 0.5–1 [[kilometer]] or more), while sunken reflectors are visible only at very close ranges due to the higher angle required to properly reflect the light. Raised reflectors are generally not used in areas that regularly experience snow during winter, as passing [[snowplow]]s can tear them off the roadways. Stress on roadways caused by cars running over embedded objects also contributes to accelerated wear and [[pothole]] formation.

Retroreflective road paint is thus very popular in [[Canada]] and parts of the United States, as it is not affected by the passage of snowplows and does not affect the interior of the roadway. Where weather permits, embedded or raised retroreflectors are preferred as they last much longer than road paint, which is weathered by the elements, can be obscured by sediment or rain, and is ground away by the passage of vehicles.