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An investigation into the potential for reducing road damage by optimising the design of heavy vehicle suspensions is described. In the first part of the paper two simple mathematical models are used to study the optimisation of conventional passive suspensions. Simple modifications are made to the steel spring suspension of a tandem axle trailer and it is found experimentally that RMS dynamic tyre forces can be reduced by 15% and theoretical road damage by 5.2%. A mathematical model of an air-sprung articulated vehicle is validated, and its suspension is optimised according to the simple models. This vehicle generates about 9% less damage than the leaf-sprung vehicle in the unmodified state and it is predicted that, for the operating conditions examined, the road damage caused by this vehicle can be reduced by a further 5.4%.

An articulated lorry was instrumented in order to measure its performance in straight-line braking. The trailer was fitted with two interchangeable tandem axle subchassis, one with an air suspension and the other with a steel monoleaf 4-spring suspension. The brakes were only applied to the trailer axles, which were fitted with anti-lock braking systems (ABS). The vehicle with the steel suspension was observed to have significantly worse braking performance than the air suspension, and also to generate larger vertical dynamic tire forces. Computer models were developed for the two suspensions, including their brakes and anti-lock systems. The models were found to reproduce most of the important features of the experimental results.