The objective of this study was to examine the effects of car-phone communication on driving performance while approaching signalized intersections, with particular emphasis on individual aggressive disposition. In a pre-screen test, participant candidates were asked to complete a questionnaire containing a driving behaviour inventory for assessment of aggression. Twelve participants (six aggressive and six non-aggressive) were recruited for the experiment. During the trials, the subjects were asked to drive across intersections or brake with or without concomitant car-phone demand (mental addition tests). Measurements included task performance (response time, correct rate), driving performance, physiological responses, and compensatory behaviour. Analysis of task performance revealed a mean correct rate of 90% for addition tests in the laboratory; however, this decreased to 87.5% in city traffic and 75.8% at intersections. The mean (SD) response time for these addition tests was 3.8 (1.9) s in the laboratory, 4.5 (1.9) s in city traffic, and 5.6 (2.4) s at the intersections. These results confirm the notion that the combination of decision making and car-phone communication at signalized intersections increases accident risk. This study has examined compensatory behaviour as drivers attempt to reduce workload. Driving speed while passing through green lights and simultaneously performing addition tests was 6.4% lower (45.1 km/h) than in normal driving. This indicates that drivers adjust their speeds to keep subjective perception of risk levels constant. When they respond to a red light, distraction causes drivers to react later; to compensate, drivers brake harder. We also demonstrate that aggressive disposition may be associated with the erosion of these safety margins, which can differ significantly between individuals. In the final analysis, safe driving relies on good driving practice, prioritization of safety, and maintenance of adequate margins. (A) "Reprinted with permission from Elsevier".
Abstract