TIME-TO-COLLISION JUDGEMENTS: VISUAL AND SPATIO-TEMPORAL FACTORS

A fundamental aspect in driving is predicting critical events in the near future. A driver on a collision course, for example, has to accurately evaluate how close s/he is to the impending collision in order to brake or swerve at the right time. In other words, s/he has to judge time-to-collision (TTC), which refers to the time that remains before reaching an obstacle, and thus to the time available for taking action. TTC is considered to be a crucial parameter in controlling avoidance behaviour. TTC is also likely to be involved in more complex judgement tasks such as overtaking or left-turn manoeuvres, where the driver has to determine whether there is enough time for the planned action. The underlying concept of temporal action control is being used increasingly often in the study of driving behaviour, which addresses the anticipatory aspects of actions such as braking, trajectory control, car following, traffic merging decisions, curve taking, stop-or-go decisions at intersections, and so on. Various equivalent terms have been employed, depending on the situation under investigation, including 'time-to-contact', 'time-to-arrival', and 'time-to-go'. The concept has also proven useful in aircraft conflict resolution and ship piloting, which involve considerably larger time frames. The current study is more specifically concerned with impending collision situations which occur when a driver is approaching a stationary vehicle. The objective was to investigate the determinants of perception-related errors which are thought to contribute to rear-end collisions (Mortimer, 1990). Rear-end collisions represent 20-25% of the total number of accidents, and 80% of rear-end crashes occur in situations where the vehicle struck was stationary or travelling very slowly. A better understanding of the visual information that drivers need to accurately judge TTC in this situation is an important condition for effective preventive action. For the covering abstract, see IRRD 896859.