This report describes a simulator study in which seven candidate in-vehicle CAS (collision avoidance system) were compared as to their effects on driving behaviour in car-following situations. The candidate CAS were combinations of criteria for system activation (`time-to-collision' vs `worst case') and subsequent warnings (a red light, a buzzer, or the action of a `smart' accelerator pedal). The simulator was programmed so that a subject during the CAS-vehicle approached a leading vehicle, driving at a prespecified speed, sufficiently often to assess behaviour in dealing with that vehicle. CAS systems affected the way in which the driving task was performed as a whole. Generally spoken the following effects were observed to be associated with the availability of a CAS: 1) A change in the distribution of headways, in particular a reduction in the occurrence of very short headways; 2) An increase in driving speed; 3) An increase in acceleration and deceleration levels; and 4) An increase in the time spent driving in the left lane of the road. This is a reprint from DRIVE Project V1041 Generic Intelligent Driver Support Systems (GIDS), Feb 1990. (A)
Abstract