Abstract: A system of the present invention for signaling panic braking of a vehicle at or above a preset rate. The vehicle has a brake pedal movable from a nondepressed position to a depressed position for braking the vehicle. The nondepressed and depressed positions correspond to open and closed positions, respectively, of a brake light switch. The vehicle energizes at least one brake light when the brake light switch is in its closed position. The system of the invention includes a mercury switch for detecting a deceleration rate of the vehicle and generates a signal representative of panic braking when the deceleration rate of the vehicle reaches or exceeds the preset panic braking rate.