a light - reflecting arrangement includes a stack of clean light - reflecting plates which are mounted on a support for gradual advancement , one after the other , into an operative position in which the respective light - reflecting plate replaces the previous one which may have become soiled while dwelling in its operating position , so that a relatively clean plate will be exposed in the operative position at all times to act as a reflector for oncoming traffic . the light - reflecting plates which have been replaced descend by gravity either to form another stack of used light - reflecting plates , or to be collected in a receptacle . the stack of the light - reflecting plates may be advanced by a pusher or by a threaded shaft cooperating with a threaded bore of the respective light - reflecting plate . the pusher may be advanced or the threaded shaft may be rotated by a spring - energized or a battery - energized motor , or by a drive which is energized by ambient pressure or temperature fluctuations .