Reducing vehicle speeds reduces the likelihood of a crash because drivers, riders and pedestrians have more time to see a hazard and react, and the breaking distance for vehicles is less. If a crash does occur, the severity is lower. There is conclusive evidence to support this but we must also understand how the regulatory speed limit influences travel speed.

So, the two questions are

  1. Does travel speed influence road trauma rates?
  2. Does the regulatory speed limit influence road trauma rates?