When a motorcycle is involved in a head-on collision, the rider continues to move forward with near to his original velocity until ejected over the front of the motorcycle. Ensuing contact with the opposing vehicle often results in serious injury, most commonly to the head and upper body. This paper examines the use of air bags as a method of forward restraint which will reduce the exit velocity of the rider.Air bag systems on two large and one small machine were tested in impacts with a stationary car and the results are compared with those from tests using an equivalent standard machine.The maximum benefit to the rider was achieved with a 120 litre air bag fitted to a large machine. This reduced the rider's kinetic energy by 82%. A similar system on a small machine reduced the rider's kinetic energy by 62%. Both the results show notable benefits to the rider. However the system on the small motorcycle is less efficient. The reasons for this and the implications for design requirements are discussed.The switch is an important component of the system. Two types of switch used in the track tests to fire the system are described. The second method, a mass/spring, system is to be developed for field trials. Details of a programme to predict and test the behaviour of this switch over a range of conditions is outlined.