An auxiliary lighting system for a helmet operable with a lighting system of a vehicle comprising a vehicle brake light, comprised of a helmet portion and a vehicle portion. The helmet portion is comprised of a helmet lighting unit, a microcontroller in communication with the helmet brake light, and a helmet transceiver in communication with the microcontroller. The vehicle portion is comprised of a supporting body, a vehicle transceiver, and an accelerometer joined to the supporting body and in communication with the microcontroller. The microcontroller is programmed with an algorithm such that the microcontroller receives a signal indicative of the relative position of the accelerometer, determines the performance capability of the accelerometer in detecting acceleration of the vehicle with respect to the Earth based upon the signal indicative of the position of the accelerometer, and presents an indication of accelerometer performance capability.