Investigation of the Influence of Various Braking Regulations on Accident-Avoidance Performance

Abstract

Passenger car braking regulations promulgated by the United States and various European countries are analyzed to determine the incompatibilities in brake proportioning that derive from the performance requirements of the regulations. Two vehicles, one produced in the U.S. and the other in Europe, with extreme loading conditions (as derive from option selection and vehicle loading) were considered. The analysis shows that the European regulations require a larger forward bias in brake proportioning than FMVSS 105-75. Computer simulations were used to predict the differences in braking performance which result from proportioning the example vehicles to comply with the different regulations. Conditions of straight-line braking, braking in a turn, and three surface friction levels were considered. In general, both vehicles were capable of achieving shorter stopping distances when proportioned to meet FMVSS 105-75 than when proportioned to comply with the European regulations, but the differences were small and could be considered trivial when a car is driven by an ordinary driver. When proportioned to meet FMVSS 105-75, the rear wheels of the two study cars sometimes locked up first, a result that the European regulations are designed to prevent. Braking-in-a-turn test procedures (which have been discussed both in the U.S. and abroad) were also studied through computer simulations and found to be relatively insensitive to the fore-aft proportioning of brake torques.