BICYCLE ACCIDENTS AND DRIVERS VISUAL-SEARCH AT LEFT AND RIGHT TURNS

The accident data base of the City of Helsinki shows that when drivers cross a cycle path as they enter a non-signalized intersection, the c learly dominant type of car-cycle crashes is that in which a cyclist c omes from the right and the driver is turning right, in marked contras t to the cases with drivers turning left (Pasanen 1992; City of Helsin ki, Traffic Planning Department, Report L4). This study first tested a n explanation that drivers turning right simply focus their attention on the cars coming from the left-those coming from the right posing no threat to them-and fail to see the cyclist from the right early enoug h. Drivers' scanning behavior was studied at two T-intersections. Two well-hidden video cameras were used, one to measure the head movements of the approaching drivers and the other one to measure speed and dis tance from the cycle crossroad. The results supported the hypothesis: the drivers turning right scanned the right leg of the T-intersection less frequently and later than those turning left. Thus, it appears th at drivers develop a visual scanning strategy which concentrates on de tection of more frequent and major dangers but ignores and may even ma sk visual information on less frequent dangers. The second part of the study evaluated different countermeasures, including speed humps, in terms of drivers' visual search behavior. The results suggested that s peed-reducing countermeasures changed drivers' visual search patterns in favor of the cyclists coming from the right, presumably at least in part due to the fact that drivers were simply provided with more time to focus on each direction.