New Understanding of Motorway Crash Risk From Newly Available Metrics

Abstract

Changes in the way the road network is used over recent decades have altered the quantity, types and causes of crashes on all roads, especially those with high traffic demand such as motorways. As “flow” increases, density rises, vehicles drive closer together more frequently, and the required reaction time is often less than the headway between vehicles. Vehicles are now heavier, wider, and taller, and in heavy traffic, drivers’ forward vision is greatly reduced. Dynamic traffic conditions (nucleations, shockwaves, congestion) make driving tasks more complex, elevating crash risk. Often conditions are beyond human and vehicle capability. Newly available metrics allow new questions to be asked, highlighting unsafe headways and clearance distances, underestimation of lane changing, and changing crash proportions. There are opportunities for new initiatives to be implemented to utilise this expanded understanding and to address the changed driving context.