Simulation Evaluation on the Rollover Propensity of Multi-Trailer Trucks at Roundabouts

The main intent of this study is to provide a simulation analysis of rollover dynamics of multi-trailer commercial vehicles in roundabouts. The results are compared with conventional tractor-semitrailer with a single 53-ft trailer for roundabouts that are of typical configuration to those in the U.S. cities. The multi-trailer commercial vehicles that are considered in this study are the A-double trucks commonly operated in the U.S. roads with the trailer length of 28 ft, 33 ft, and 40 ft. The multi-body dynamic models for analyzing the rollover characteristics of the trucks in roundabouts are established in TruckSim®. The models are intended to be used to assess the maximum rollover indexes of each trailer combination subjected to various circulating speeds for two types of roundabouts, 140-ft single-lane and 180-ft double-lane. The simulation results suggest that the 40-ft double has rollover speed thresholds 2-9 mph lower (more vulnerable to rolling over) as compared with the conventional 53-ft semi-trailer-truck. The lower roll stability for the 40-ft A-train configuration is attributed to its pintle-hitch coupling that allows for a certain amount of roll degree of freedom between the front and rear trailers. In addition, the worse tracking performance of the 40-ft double due to its longer wheelbase contributes to the heavier use of truck apron, greatly increasing the chance of rollover. The results also indicate that the 28-ft and 33-ft double-trailer trucks possess better maneuverability (less off-tracking) and can tolerate the rollover speed 1-3 mph higher than that of the 53-ft single-trailer truck. Furthermore, it is found that increasing the trailer from 28 ft to 33 ft results in the truck slightly less prone to rollover crashes, because of their longer wheelbase providing a slight amount of additional roll stability.