Brake force requirement study: driver vehicle braking performance as a function of brake system design variables : Mortimer, R.G., Segel, L., Dugoff, H., Campbell, J.D. and Jorgeson, C.M.Abstr. in US Government Research and Development Reports (Report Nos. PV. 192 258 and PB. 193 259)

Abstract

The objective of this study was to define those brake characteristics, within the space bounded by the relationship between brake pedal force and vehicle deceleration, which lead to acceptable driver-vehicle performance. A driver-vehicle braking test was performed in which the deceleration/pedal force ratio, the pedal displacement, the surface-tire friction, and driver characteristics (age, weight) were systematically varied in order to determine the influence of these variables upon minimum stopping distance and other performance variables. The tests that were performed on a low coefficient of friction surface showed that high values of deceleration/pedal force gain result in large number of wheel lockups and lower mean deceleration in bringing the vehicle to a stop, compared to intermediate or low deceleration/pedal force gain levels. Tests conducted on intermediate and high coefficient of friction surfaces showed that high and intermediate deceleration/pedal force gains produced greater mean decelerations and greater frequencies of wheel lockups than lower gain systems. The frequency of loss of lateral control was significantly greater with the high deceleration/pedal force gain brakes on all surfaces than with lower gains. There were minor benefits of 2.5 inch pedal displacement compared to zero inches. Potential brake failures and their effects upon pedal force requirements were analyzed. The implications of the findings for a vehicle braking standard were shown in terms of deceleration/pedal force gain and pedal force.