This paper describes about Hill Starting Aid (HSA) system for mechanical transmission vehicle designed to retain braking force of service brake after vehicle stops and to release this braking force automatically at the time of vehicle starting.By this system, the driver can start on slope as easy as starting on level road, because it relieved driver of operating hand brake lever and quick movement of his right foot from brake pedal to accelerator pedal. So, this system alleviates fatigue of drivers and also efficient for inexperienced drivers. As this system is basically brake force holding system, it is effective for prevention of successive collision from behind too. In this way. HSA system is very suitable for Japanese traffic condition which there are many slopes and heavy traffic in city.