The braking characteristics have been studied on 100 heavy tractor/truck-trailer combinations in each of four countries. To achieve results representative for the four vehicle populations, police and vehicle inspection officers selected the vehicles randomly from the normal traffic flow on suitable roads. Both the overall deceleration performance and the brake force distribution were measured directly by driving and dynometer tests. Also recorded were weight distributions, brake and wheel size, push rod stroke, load sensing valve amplitude, etc. Results include plots as well as linear correlation and regression coefficients of functions such as: load sensing valve adjustments versus relative load; deceleration versus control pressure; trailer versus truck deceleration performance; deceleration measured on the road versus computation from dynometer data; brake force versus push rod stroke. Comparisons are made between trailer types, load weight classes, and between countries considering their distinct differences in legislative requirements. Wheel lockup observations are related to simultaneous deceleration and control pressure measurements. The deviations between ideal and recorded influence from load sensing devices are evaluated. No Antilock Brake System (ABS) was found in this vehicle sample (data from 1986-1987). (A) For the covering abstract of the conference, see IRRD 837684.
Abstract