A lighting system adapted to mount on a motorcycle or bicycle helmet. The lighting system includes a one or more accelerometers coupled to the helmet and a processor adapted to process the signals from the accelerometers. The accelerometers may be mounted to the helmet, or the motorcycle or bicycle. The lighting system further includes a light mounted on the helmet that is responsive to the processed signal such that the light illuminates as result of a deceleration force. The system may also include filtering software to remove helmet motion artifact and other noise from the signal. Remote wheel speed indicators may also be used in conjunction with or in place of the accelerometers. Mounting tabs may also be included to releasably attach the lighting unit to the helmet.