This recommended practice encompasses the significant factors which determine the effectiveness of a seat system in limiting spinal injury during vertical impacts between, the rider and the snowmobile seat system. The recommended practice is intended to provide a tool for the development of safer snowmobile seats. It is recognized that the seat is only a portion of the entire vehicle protective suspension system. It is, however, usually required that the seat serve as added protection to the suspension system, since the latter may “bottom out” during a severe impact. The term “seat” refers to the occupant-supporting system not normally considered part of the vehicle suspension or frame system. In some cases, it may include more than the foam cushion. This recommended practice provides the minimum requirements for performance of a general seat system, and a description of specific means of evaluating the shock absorbing characteristics of foam seat cushions using a specific testing, procedure and a companion safety evaluation chart. The recommended practice relates measurable mechanical data attainable in controlled laboratory testing to known biomechanical data on living subjects. The test input and means of interpreting the results are unique to the seats of typical recreational snowmobiles as illustrated in SAE J33. Therefore, this SAE Recommended Practice should not be applied to evaluate seats of snow vehicles of significantly different design, dimensions, construction, or intended usage from the typical recreational snowmobile illustrated in SAE J33. The test input and means of interpreting the results are unique to snow mobiles and snowmobile seats. Therefore, this SAE recommended seat is to be used for snowmobile seats only, and is not to be used to evaluate seats on any other type of vehicle.