Car use is growing rapidly in many countries. The resultant increase in interaction between cars, heavy vehicles (such as trucks or buses) and vulnerable road users often leads to conflicts and more crashes.

Car occupants are also at risk themselves, particularly in higher speed environments. Even in the most modern of vehicles, the chance of surviving a side impact with a tree or post reduces dramatically above 30 km/h, while the chances of survival are low above 70 km/h for a head-on crash with a similar vehicle. For less modern vehicles, or in collisions with vulnerable road users, survival speeds in a collision are far less.

While people will always makes mistakes, there are many road related factors that influence the risk of crashes. It is often easier, cheaper and more effective to improve safety through a change to the road environment than it is to change driver behaviour, so improvements in the road system are an important means of improving road safety.

Road related contributing factors to crashes include:

• inappropriate speeds.
• uncontrolled movements and turns, especially at intersections and access points.
• lack of separation of vehicles or road users of different size (e.g. lack of facilities for pedestrians and cyclists).
• lack of separation for vehicles travelling in different directions (e.g. lack of median barriers).
• lack of advanced warning of hazards.
• inadequate information to enable road users to negotiate the roadway safely.
• presence of hazards, particularly at the roadside (e.g. utility poles and trees).
• poor road surface.