The speed of the vehicles involved in collisions is one of the most significant factors that affect the severity of road-traffic accident injuries. A review of speed regulations around the world reveals that in addition to legal requirements, speed limits should be set considering road conditions, crash scenarios, traffic conditions, infrastructure quality, and the biomechanical tolerance levels of the human body. This study presents an analysis of vehicle crash speed, crash scenarios, and injury risks to explore how crash severity affects the injuries sustained by pedestrians and passengers. This study also examines speed limit enforcement practices around the world. The findings show that crashes above 50 km/h significantly increase the risk of serious injuries (MAIS3+F), and the risk of MAIS3+F level injuries is even higher in the side impact and head-on impact scenarios.

Considering that frontal impact scenarios can have fatal effects, in countries such as Sweden, travel speeds of 80 km/h are appropriate for undivided roads. On heavily trafficked highways and intersections, a speed limit of 60 km/h is appropriate. For rear impact scenarios, it is advised that the closing speed between vehicles is no more than 30 km/h to limit whiplash injuries. Regarding pedestrian safety, it is imperative to keep speed limits as low as possible in school zones, city centres, and pedestrian crossings. Research has shown that speeds above 30 km/h significantly increase the risk of death for pedestrians, while speeds above 50 km/h pose a crucial risk of injury and death for pedestrians. In many European countries, maximum speed limits on urban roads have been reduced to 30 km/h, with pedestrian safety in mind.

Based on the current knowledge and literature, this study provides guidelines for setting speed limits to reduce the risk of injury for crash severities that the human body can biomechanically tolerate. An overview of the types of injuries that occur in accidents, speed limits and speed parameters specific to the crash scenarios are outlined.