Driver Misperception of Maneuver Opportunities and Requirements

Misperceptions of the time available or time required for various driving maneuvers under a range of conditions were studied. In the laboratory experiment, research participants viewed video scenes of a wide variety of situations and made judgments about when some event would occur (e.g., approaching vehicle reaches them) or when some maneuver would be completed (e.g., own vehicle clears roadway when making a crossing maneuver). Participants' judgments were compared with objectively determined values. A parallel on-road experiment, using similar procedures and a subset of the laboratory situations, was used to validate and benchmark the laboratory findings. The study found a general tendency for people to underestimate the time required for a maneuver. This misjudgment is safety-critical, because it may lead to decisions to accept maneuver opportunities that actually afford a smaller margin of error than the driver perceives. Such misestimates were particularly common for judgments of the time to achieve the prevailing traffic speed during turning or merging maneuvers, and for the time until one's vehicle reaches an intersection ahead. For judgments of the time available for a maneuver, people more frequently felt they had less time than they actually did, so would be less likely to attempt a maneuver. However, even for time available judgments, there were meaningful numbers of safety-critical errors. Some situations emerged as particularly meriting consideration for safety countermeasures. These included: (1) approach to signalized intersections; (2) turns onto higher-speed roadways; (3) freeway merges; (4) passing; and (5) headway maintenance. A number of promising countermeasure ideas addressing these issues were developed and recommended for formal evaluation.