The safety regulations and rating systems in various parts of the world have not achieved harmonisation. A good example is the differing requirements of side impact protection. This investigation started by a review of existing vehicle regulations and crash rating tests around the world, especially in Europe, North America and China. The reviewing contains the crash tests history, current state and future directions. Then focused on the main differences of each side impact tests, twelve side impact test activities are compared in detail among Europe, North America and China. Potential influences of the test differences on vehicle design were identified. Some possible solutions for side structure improvement are proposed in the last chapter.