Stability and braking performance analysis of bus/pony-trailer combination vehicles

In this paper, the stability and braking performance of two bus/pony-trailer combination vehicles (40-ft and 45-ft wheelbase buses) are examined by computer simulation. Two simulation models. the Yaw/Roll model and the simplified straight line braking model developed by the University of Michigan Transportation Research Institute (UMTRI), were used to evaluate the complete set of performance measures. The performance measures obtained are checked against specific performance criteria. In response to an expressed interest in the bus/pony-trailer hitch load, the effects of the trailer's wheelbase and tandem axle spacing variations on the performance measures are examined. The study clearly indicates that the dynamic performance of the two buses would be affected slightly by towing the pony-trailers. The performance of the combination vehicles is acceptable, in comparison with a standard 5-axle tractor and semi-trailer, if appropriate pony-trailer wheelbase and axle spacing are selected.