This paper outlines the most important characteristics of the practical type air bag now being developed by Nissan Motor Co., Ltd. It explains the results of various occupant protection tests conducted at 16 to 64 km/h (10 to 40 mph) speeds, and the related problems we have encountered. It further discusses the effects of several type of occupant protection systems installed on small-sized cars and the relationships between those effects and limited crash speeds. An examination and analysis of air bag performance test results is also included.Despite all efforts made, there yet remain several problems to be solved. For example, (a) in high-speed collisions it is difficult to reduce femur load by means of air bag systems alone; (b) passengers such as three-year-old infants and 5th percentile female adults display a tendency toward submarining: (c) when the environmental temperature is extremely low, it is difficult for the air bag to meet the MVSS Occupant Protection Requirements.