In Swedish statistics from 1985 and 1986, the percentage of "oncoming vehicle" accidents is four times greater on snowy/icy roads (16%) than on dry clear roads (4%). The percentage "rear end" accidents is the same (6%) for both road conditions. Also the fatality numbers (364 people in "oncoming vehicle" versus 26 in "rear end" accidents) indicate that more emphasis should be put on instability and skidding problems (typical for oncoming vehicle accidents) than on braking distances and steering-while-braking problems (rear end accidents). Vehicle dynamics show that the cornering performance of the rear wheels must be superior to that of the front wheels, if a car is to be stable at all speeds. This is illustrated by some hydroplaning fatality cases, where the tyre pattern was much deeper at the front than at the rear. Since traction or braking forces reduce the side force, skid recovery will be more difficult in a front wheel driven car, if the driver depresses the clutch pedal before countersteering. Experiments with experienced drivers offered an explanation to why such a behaviour still is recommended in many driver training courses. Influence on stability from vehicle design and equipment is being even more pronounced with antilock (ABS-) brakes, 4 wheel steering, cruise control, etc. This must be considered in research on vehicle black spots in accidents, in vehicle inspection and testing, and in driver training programs. (A) For the covering abstract of the conference, see IRRD 837684.
Abstract