Minimum Time to Situation Awareness in Scenarios Involving Transfer of Control from an Automated Driving Suite

This research assessed the impact of vehicle automation on a driver's ability to anticipate latent threats and to detect materialized hazards on the forward roadway. In particular, the minimum alert time before transfer of control was determined. This was the minimum time required after an autonomous driving suite (ADS) had been in full control of a vehicle for the driver to reacquire the same level of situation awareness that he or she had when in full control of the vehicle. This simulator study included five treatment conditions during which drivers either were always in complete control of their own vehicle (control) or were required to resume control at 4 s, 6 s, 8 s, or 12 s before the appearance of a latent hazard (transfer). While the vehicle was in autonomous mode, the drivers performed an in-vehicle task for more than a minute and were told not to glance at the forward roadway. Analysis of eye movements showed that drivers in the control condition detected nearly 40% more hazards compared with drivers in the shortest transfer condition. The results indicated how long before control was transferred from the ADS back to a driver that the driver should be told that a transfer would occur, if the driver were to have full situation awareness. Unlike previous studies, this study both ensured that the driver was not watching for hazards while the ADS was in control and used a measure of situation awareness (hazard anticipation) that was closely linked to the actual understanding a driver had of the threats present in a given scenario.