In the course of some braking experiments, a car was heavily braked on a dry surface from a speed of about 60 mile/h. It swung round violently and overturned. A theoretical study of the incident suggested that the overturning could be explained by the car being braked within a small critical range of brake pressures, the rear wheels losing adhesion and causing the car to spin, thus building up a sideways acceleration and a rotation in roll. This might have been sufficient to overturn the car on a surface having a high coefficent of friction. The study also showed that at least two other factors might be expected to increase the tendency to overturn viz., if the braking were reduced as soon as most of the car's weight came on to the offside wheels or if brake fade occurred at the front wheels. Because of these different factors, it would seem likely that cars of different design could overturn given appropriate conditions. Recent designs have usually had a lower ratio of height of centre of gravity to track than the 0.46 of the car in question and this is probably the most effective way of preventing cars from overturning. The most important feature of the incident from the point of view of road safety is probably the initial loss of directional control; on the road it seems likely that most cars would strike something before they had reached the point of overturning or if the object struck happened to be a kerb, this would greatly increase the tendency to overturn.


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    Title :

    The Overturning of Cars as a Result of Severe Braking


    Contributors:
    R. N. Kemp (author) / I. D. Neilson (author)

    Publication date :

    1967


    Size :

    27 pages


    Type of media :

    Report


    Type of material :

    No indication


    Language :

    English




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