A computational method was employed using data from a field operational test of Adaptive Cruise Control (ACC) to estimate the relationship between an ACC system's deceleration authority and the frequency of driver intervention. Systems posing an infrequent need for intervention are hypothesised to influence the vigilance of the ACC driver, recognising that humans are less ready to execute a rarely-occurring task. For ACC controllers having high deceleration authority, the results show that most normally-occurring conflicts can be managed automatically by the system, resulting in a very low frequency of events requiring driver brake intervention. ACC products offering 0.3g of deceleration authority, for example, will require intervention on the order of once per thousand miles when operated under moderate traffic conditions on US freeways. It is suggested that vigilance may tend to lapse under such conditions, posing a safety challenge for some drivers.
Abstract