Factsheet: The relation between speed and crashes (UN)

SWOV Fact sheet | The relation between speed and crashes

The exact relation between speed and crashes depends on many factors. However, in a general sense the relation is very clear: if on a road the driven speeds become higher, the crash rate will also increase. The crash rate is also higher for an individual vehicle that drives at higher speed than the other traffic on that road. As speeds get higher, crashes also result in more serious injury, for the driver who caused the crash as well as for the crash opponent. The injury severity of the vehicle occupants in a crash, for example, is not only determined by the collision speed, but also by the mass difference between the vehicles and by the vulnerability of the vehicles/road users who are involved. In a crash between a light vehicle and a heavier one, the occupants of the lighter vehicle generally are considerably worse off than the occupants of the heavier vehicle. Even more so this is the case for pedestrians, cyclists and moped riders in crashes with (much) heavier motor vehicles.

Speed is one of the basic risk factors in traffic (Wegman & Aarts, 2006). Higher driving speeds lead to higher collision speeds and thus to severer injury. Higher driving speeds also provide less time to process information and to act on it, and the braking distance is longer. Therefore the possibility of avoiding a collision is smaller. In short: high driving speeds lead to a higher crash rate, also with a greater likelihood of a severer outcome (Aarts, 2004; Aarts & Van Schagen, 2006). However, not everything is known yet about the exact relation between speed and road safety, and the conditions that influence this relation. This makes it difficult, for example, to calculate the exact effects of specific speeding measures. This fact sheet summarizes the most recent insights in the relation between speed and road safety.