Abstract: A sudden-stop brake-light warning system (10) that causes the brake lights (56) of a vehicle to intermittently pulsate. The pulsation of the lights (56) is achieved by a flashing brake-light circuit (12) that is only activated when the brake pedal is depressed during a panic stop. The circuit (12) consists of a mercury switch (51), located in an inertia operative switching circuit (16), that closes only when the brake switch (54) is depressed during a panic stop. When the switch (54) closes, the power from the vehicle battery (52) is applied to the gate of a silicon controlled rectifier (CR1) located in a silicon controlled rectifier circuit (18). The energizing of CR1 enables a multivibrator circuit (14) connected via a relay driven transistor (Q3) to the coil (20A) of a relay (K1) located in a relay drive/relay circuit (20). The relay is pulsed in accordance with the time constant of the multivibrator and as the coil (20A) pulses, so are the brake lights (56).