Simulation of accident risk displays in motorway driving with traffic.

The study used a vehicle-based driving simulator to evaluate two graphical displays, one showing risk probability in terms of safety margin (Time Headway, TH), and one showing risk severity in terms of Kinetic Energy (KE). Twenty-seven subjects were randomly allocated to one of three experimental conditions: Control, TH, and KE. Subjects undertook three driving tasks (ABA design). For the second driving task in the TH and KE conditions, subjects drove in the presence of their respective feedback displays. Measures of TH and KE levels were taken, as well as subjective measures of risk and task loading. It was found that the KE display was more effective than the TH display in reducing the proportion of time subjects spent at short headways. The KE display was also effective in reducing the proportion of time subjects spent at high speed. The KE display appeared to affect the perception of risk (severity of potential accidents). It was concluded that further research evaluating displays that combined the positive effects of both parameters within a single representation display is needed.