Abstract: A warning system for a vehicle in which a control circuit is actuated to turn on selected exterior lights of the vehicle when the horn switch is actuated. The control circuit includes a relay that has a first contact connected to the battery, a second contact conductively connected to the first contact when the control circuit is actuated, and a plurality of unidirectionally conductive circuits, each connected in series between the second contact and selected electric lights and polarized to be conductive in the direction to conduct operating current from the battery to those lights to turn them on when the horn switch is actuated.