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Run Off Road

Run-off-road crashes are common, especially in high speed areas. They occur at bends and on straight sections of road. In high speed environments they can have severe outcomes, particularly if an object is hit (for example trees, poles, pedestrians) or there is a steep embankment or cliff.

Research shows that the survival rate for a vehicle hitting an object head-on reduces dramatically above 70 km/h, while a vehicle side impact into a pole or tree is greatly reduced at speeds above 30 km/h. Therefore, the consequences of running off the road above this speed will often be severe. The consequences for motorcyclists can be severe at even lower speeds.

On the other hand, an errant vehicle dropping off the roadside can result in severe casualties due to rollover and deformation of the vehicle body. The consequences increase with the height of the fall and presence of water body or other hazards along the trajectory.

Public transport vehicles running off the road can result in multiple severe casualties due to increased tendency of rollover and severe deformation of the vehicle body. Passengers in these vehicles are often unrestrained and the bodies of these vehicles are relatively fragile.

Run-off-road crashes can lead to secondary events if an errant vehicle encroaches onto another road, a railway, or crowds of people. Collision with buildings, bridge piers, houses or other structures may lead to collapse or structural damages. Catastrophic secondary events can happen if dangerous goods vehicles run off the road.

Engineering treatments generally act to assist drivers to stay on the road (e.g. improvements to the road surface, advanced information about curves and their severity), alert drivers that they are leaving the road (e.g. rumble strips), improve the chance of recovering control of the vehicle if it does leave the road (e.g. shoulder treatments), or reduce the severity of the outcome if a vehicle does leave the road (e.g. clear zones, crash barriers and attenuators).

Typical factors which may add to run-off road crash risk include:

Name Cost rating Effectiveness
Delineation Low 10 – 25%
Lane Widening Medium to High 25 – 40%
Median Barrier Medium to High 60% or more
Realignment – Horizontal High 25 – 40%
Realignment – Vertical High 10 – 25%
Roadside Safety – Barriers Medium 40 – 60%
Roadside Safety – Hazard Removal Low to Medium 25 – 40%
Rumble Strips Low 10 – 25%
Paved Shoulder Medium 25 – 40%
Sideslope Improvement Medium 10 – 25%
Skid Resistance Low to Medium 25 – 40%
Speed Management Medium 25 – 40%
Traffic Calming Medium to High 25 – 40%

Related Images

  • A bus that had a run-off road crash in Malaysia. Image credit: John Mumford
  • A motorcycle run-off road crash into a tree. Image credit: iStock
  • A motorcyclist wearing a helmet and protective clothing in a crash. Image credit: iStock
  • A run off road crash in Kenya. Image credit: iRAP
  • A run off road crash involving a car and tree. Image credit: iStock
  • A run-off crash. Barrier end terminals must be designed to minimize risk upon impact. A crash attenuator would be a suitable end treatment in this case. Image credit: JP Research India
  • Vehicle occupant Star Ratings by road user type based on a 358,000km sample of roads across 54 countries. Image credit: iRAP
  • Motorcyclist Star Ratings by road user type based on a 358,000km sample of roads across 54 countries. Image credit: iRAP
  • Off Carriageway to left graphic
  • Off Carriageway to right graphic
  • Overturned truck in Assam, India. Image credit: A. Tiwari
  • Run off road crash in Bangladesh. Image credit: Greg Smith
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