Driver behaviour at horizontal curves
Thesis DisciplineCivil Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Studies relating accident occurrence to horizontal curve geometry indicate a strong association between the radius of horizontal curves and accident occurrence, but the individual effect of horizontal curvature on safety is still uncertain. The preponderance of human error as a contributory cause of accidents has led to a growing interest in research on driver behaviour. The human factor in road safety is discussed and literature on driver behaviour on horizontal curves is reviewed. A study involving unobtrusive observation of driver behaviour at two curves (an isolated curve and a reverse curve) before and after realignment was carried out. Data on driver behaviour was collected by continuous video-recording of each subject vehicle as it moved through each curve. Lateral placement and speed data along the curve were extracted from the video record, and the path radius and sideway force coefficient at the mid-point of the curve were estimated. The observed driver behaviour is discussed. The results of the study were checked against the underlying design assumptions, which are shown not to be completely and universally valid. The evaluation of the realignment, based on driver behaviour and the sideway force coefficient, and the accident records show that there was an overall improvement in the margin of safety at all the curves (except one). The results do not support the concept of risk homeostasis, although there is evidence of risk compensation.