The purpose of this study was to investigate the temporal limitations of the driver's steering avoidance of obstacles which were stationary but appeared suddenly ahead of the vehicle, with appearance timings directly controlled in a driving simulator. Under conditions where the event was expected, all 25 drivers completed obstacle avoidance successfully when the time margins were longer than 3.0 seconds, though no driver was able to avoid the obstacle in cases where the time margin was 1.2 seconds or shorter. Under conditions where the event was unexpected, around half of the drivers failed to avoid the obstacle where the level of visible distance and the driving speed had allowed all drivers to avoid the expected obstacle. From these findings, it was concluded that a time margin longer than 3.0 seconds would be effective for ensuring successful steering avoidance if the driver was anticipating the potential appearance of any obstacle.
Abstract