When a driver has accidentally travelled onto the road shoulder the risk of crashing will be less if the vehicles can either stop on the shoulder or safely travel back into the traffic lane.
The vehicle will be better able to do both of these things if the shoulder is wide enough and if the vehicle tyres are able to grip the surface of the shoulder.
A sealed road surface provides the best grip for tyres. When a vehicle leaves the road, and especially when this happens at high speed, stopping and/or steering the vehicle back onto the road will be easier if the vehicle tyres are able to grip the shoulder surface.
An adequate shoulder width makes it easier for a driver to steer the vehicle back onto the road at a shallower angle, reducing the chances that the driver will ‘overcorrect’ and travel into oncoming traffic. Shoulders that are too wide create a hazard if they are used as an additional lane.
- Reduce run-off-road and head-on crashes.
- Wider shoulders allow vehicles to pull off the road in emergency situations and have clearance from through traffic (however crashes can occur when vehicles attempt to rejoin the traffic).
- Sealed shoulders provide a safe cycling space, and can be marked as bicycle lanes.
- Sealed shoulders provide structural support to the road pavement.
- Sealing can reduce ‘edge drop’ (where there is a difference between the height of the road surface and the height of the shoulder). Edge drop can make it harder for vehicles which have left the road to get back onto the road.
5 years - 10 years
Potential casualty reduction