Citation

Bullen F, Ruller J. Road Transp. Res. 1992; 1(4): 74-86.

Copyright

(Copyright © 1992, Australian Road Research Board)

DOI

unavailable

PMID

unavailable

Abstract

Data pertaining to the prediction and evaluation of the emergency braking response of vehicles operating under Australian road conditions is unavailable or very dated. The project studied the effects of pavement surface, tyre type and pressure on the emergency braking capacity of a typical family sedan. It was found that tyre type had a varying but small effect, dependent upon the wet/dry condition of the pavement. Tyre pressure did not appear to influence the braking distance to any great extent in either wet or dry conditions. The accuracy of predictive and post-braking methods of determining braking distance was examined. A 'chalk gun' braking distance method used by police accident units for determining pre-accident vehicle speeds appeared satisfactory as all components of the drag factor, which is responsible for vehicle stopping, are considered. The typical relationship of reduction in drag factor with increase in vehicle speed was obtained using the chalk gun. A VC.200 computer within the vehicle was used to measure average deceleration during braking as an estimate of drag factor to assist in determining pre-accident braking speeds. The use of average deceleration as an estimate of drag factor resulted in excessively conservative estimates of vehicle speed at braking. The VC.200 data did not exhibit the general trend of reduction in drag factor (as evaluated by average deceleration) with increase in vehicle speed at braking.

Language: en