Abstract: The improved system employs a logic unit coupled to the conventional brake switch, the turn signal and a clutch, or, optionally, an emission system low speed switch, and/or one or more safety-affecting parameters, viz., light level or other ambient conditions including fog or precipitation as sensed by applicable switch positions, to control the mode of illumination of the auxiliary light. The auxiliary light has the capability of operating in two illumination modes: steady-state as an extension of the main brake lights or flashing. Flashing of the auxiliary brake light can occur concurrently with or independent of the illumination state of the conventional main brake lights. Concurrent activation of both the brake and clutch or, optionally, the emission system low speed switch sets the flashing mode for the auxiliary high mount light. When one or more safety-affecting parameters are present, depressing only the brake pedal is necessary to set the flashing mode.