Abstract: A bicycle stop light is energized by the contraction of the hand operated caliper brakes and includes a first contact member mounted on and insulated from the flexible brake actuating cable extending between the proximal ends of the brake caliper levers and anchored to a first lever end, the cable sheath being anchored to the second lever end by an axially adjustable threaded sleeve affixed to the sheath. The first contact member is spring biased toward the threaded sleeve which defines a frame grounded second contact member, the first contact member being grounded in series with a battery and stop light to the bicycle frame.