Wheelbase Influence on Performance of Tractor-Semitrailer Combinations

A commonly seen vehicle combination on the European road network is the tractor-semitrailer with a maximum legal length of 16.5 m. In Nordic countries longer tractor-semitrailers are allowed, which makes tractors with larger wheelbase an appealing option. Concerns have been raised that shorter tractors have poorer performance and are involved in more accidents than the Nordic equivalents, especially in winter conditions. To answer the raised questions and concerns, this paper investigates the effects of a tractor wheelbase length on performance of a vehicle combination, as well as other influencing factors such as lubrication of the fifth when, loading condition and road friction level. Six tractor-semitrailer combinations with different wheelbases and axle configurations are modeled and compared. Nordic (truck-dolly-semitrailer) and B-double (tractor-link trailer-semitrailer) combinations, which are common in Nordic countries, are also used as reference vehicles in the comparison. Three maneuvers are simulated to provoke dangerous situations, namely braking with all wheels in a curve, engine braking in a curve and a fast single lane change. The results show that wheelbase alone does not have a major role in the outcome of the simulations, but a combined influence of axle configuration, wheelbase, fifth wheel position and axle loads determines the vehicle performance. Factors such as existence of a working anti-lock braking system or lubrication of the fifth wheel have a large effect on the vehicle performance, under the tested conditions.