Optimum speeds on rural roads based on ‘willingness to pay’ values of road trauma.

The optimum speed is one which minimises the total social costs of the impacts of speed, including the costs of road trauma, travel time, air pollution emissions, noise and vehicle operating costs. Previous research has estimated the optimum speeds for cars and trucks on various classes of rural roads in Australia, based on ‘human capital’ costs of road trauma. This paper presents estimates of the optimum speeds if the changes in road trauma are valued using recent ‘willingness to pay’ estimates. If speed limits were set so that all cars and trucks travelled at their optimum speed on each class of road, there would be a 34% reduction in crash costs and an overall 3.4% reduction in total social costs on rural highways in Victoria.