Control circuit for controlling the supply of power to hazard warning lamps

A method of controlling the supply of power to plural hazard warning lamps (10,12) of a motor vehicle or the like comprises outputting current for operating the hazard lamps so as to be simultaneously illuminated, wherein said step of outputting current is arranged such that a respective one of said lamps is powered at a time when one or more other of said lamps is powered, whereby information indicative of current output for each of said lamps can be obtained.