This chapter reports an experimental evaluation of some collision avoidance systems (CAS) by the GIDS project of the DRIVE programme, and discusses their implications for driver behaviour. CAS systems must be able to: (1) measure objects' distances, bearings, and relative velocities; (2) have an appropriate criterion for system activation; (3) specify appropriate actions; and (4) appropriately divide responsibility for action between the system and the driver. System actions include: (1) continuous displays of critical parameters such as time-to-collision (TTC); (2) warnings; (3) suggested driver actions; and (4) system actions that the driver can or cannot overrule. The following candidate CAS systems were tested, in terms of their effects on driver behaviour in a car-following task performed on a simulator: (1) three systems combining a TTC criterion with a warning; (2) three systems combining a worst case criterion with a warning; (3) a minimal CAS, using a continuous display. The three warning systems used were: light, buzzer and 'smart gaspedal'. Each subject performed a car-following task, with and without a simulator. The results showed that the CAS's tested usually reduced the number of short headways and increased average speed. However, speed became more variable, and, in some situations, risk of another type of collision was increased. The availability of a CAS changed driving behaviour in at least four ways.
Abstract