A comparative analysis of detailed road crash data from four different environments is presented. Three of the studies were on-scene investigations of crashes from Adelaide, Australia; Birmingham, and Worcestershire, England. The fourth set of data was taken from ACIR reports by Cornell Aeronautical Lab., Inc. of predominantly rural crashes in the United States. Where necessary the data were reanalyzed so that the variables being discussed were compatible. Comparisons are drawn between speeds at impact, areas of impact, vehicle damage severity, seated position, injury severity, anatomical injury distribution, and causes of injury for the four sets of data.The results show that there are considerable similarities between rural crashes in England and the United States, and urban crashes in Adelaide and Birmingham. Further, urban crashes have quite distinct characteristics from rural crashes. In urban collisions, speeds are low (22 mph), side impacts are frequent and lead to many injuries from the door structures. There are fewer injuries per person. In rural crashes impact speeds are higher, there are more frontal impacts and rollovers, and more injuries per person. The instrument panel, steering assembly, and windshield are the major causes of injury, regardless of whether the windshield is toughened or laminated glass, and ejection occurs with considerable frequency. The rank order of components which cause injury is discussed. The rank order changes when minor injuries are excluded.The research shows that the priorities for improvements vary with the environment, and a detailed knowledge of the crash circumstances in each country is required before design changes can have their maximum effect.