Experimental Investigations on the Braking Performance of Motor Vehicles

Abstract

This paper contains the results of experimental investigations on the braking performance of different classes of road vehicle when new and as they are used on the roads. Measurements were made of the shortest braking distance obtainable on a dry surface and of the behaviour of cars during emergency braking on straight roads both when the brakes were properly adjusted and when they were deliberately put out of adjustment to simulate the condition of some braking systems observed on the road. The results confirmed earlier experiments with models but also showed that if the time interval between the front wheels locking and the rear wheels locking exceeds a certain critical value, this has an important influence on the behaviour of the braked car. Measurements are described on the braking performance of commercial vehicles and how this is affected by loading and by the characteristics of the braking system. Other investigations on the braking performance of public service vehicles, motor cycles, and motor-assisted cycles are also described. Certain discrepancies in the published figures for the braking performance of vehicles are discussed. The paper concludes with a summary of the braking problems which merit the attention of vehicle designers.