Abstract: Apparatus (2) for indicating the formation of ice on a road (4), which apparatus (2) comprises a plurality of road marker reflector devices (6) for reflecting light from vehicles, a temperature sensor (8) for sensing temperatures above and below those temperatures at which ice forms on the road, and a solar powered electricity providing device (10), and the apparatus (2) being such that: the road marker reflector devices (8) are of a first colour at temperatures above which the ice may form, and are of a second colour at temperatures below which the ice may form; the road marker reflector devices (6) change between the first and second colours in response to an electric current; and the road marker reflector devices (8) change from the first colour to the second colour and from the second colour to the first colour when the electric current is a non-continuous electric current, whereby a continuous electric current is not required to maintain the road marker reflector devices (6) in the first or second colour