ABSTRACT
A driver is following a lead vehicle at a constant headway with the intention of merging into a lane on the freeway. While he glances over his shoulder for an appropriate gap to merge into, the lead vehicle suddenly brakes. When he looks back at the lead vehicle, he cannot brake in time and a rear-end crash occurs. Alternatively, the driver could be reading a text message on his cell phone or turned around to argue with a passenger in the back seat when the lead vehicle suddenly brakes in stop-and-go traffi c. In each scenario, the driver is looking away from the forward view. The fi rst example is perhaps more interesting because it illustrates that the driving task itself, not just secondary tasks, can be distracting. Although the argument could be made that a good driver is always aware that an emergency situation could occur at any time, it is very diffi cult, if not impossible, to remain vigilant and pay attention to all relevant sources of information while driving. In particular, the simultaneous occurrence of an unexpected event and eye diversion has been demonstrated to play a key role in the causation of crashes and near-crashes.1
