In our previous research, we found that drivers when engaged in straight-road driving, and also braking, tend to look in the direction of their intended movement regardless of speed or expertise (Rogers, Kadar, & Costall, this issue). Furthermore, gaze direction is highly constrained in braking, suggesting that speed control might be based on global optic flow. This study further investigates gaze when drivers are braking in front of a vertical barrier and either approaching the barrier orthogonally or from the right or the left. These three different directions of approach entail three different potential points of collision: the nose of the car, or the front right or left wheel. In all conditions, drivers directed their gaze in the direction of their movement. However, in the case of nonorthogonal approach, the drivers at the very end of their approach shifted their gaze away from their direction of travel and toward the potential collision point on the barrier. On the basis of these findings, we propose that drivers tend to rely on global optic flow to control their speed, but can also control speed by the local rate of optic expansion around the point of fixation (i.e., the point of potential collision). (Author/publisher)
Abstract