Wear and tear on public roads caused by heavy commercial vehicles incurs an annual maintenance cost of about 850 million. Estimates have shown that savings of at least 50 million could be achieved if the best available suspension systems were fitted to vehicles. Instrumented vehicles have been tested on both public roads and the TRL test track to establish the performance of current types of suspensions fitted to heavy commercial vehicles. Measurements have also been made over bridges and during track tests to simulate bridges. Results have shown fundamental differences in the characteristics of steel and air sprung suspension systems which explain why air sprung systems produce considerably lower dynamic wheel loads than their steel sprung counterparts. The use of "road friendly" suspensions could reduce road wear significantly; by using an air sprung suspension instead of steel on a semi-trailer wear would be reduced by about 10 per cent on a well maintained non-motorway road. This assumes that road loads are distributed evenly along the road surface. However if loads are found to be distributed as clusters producing "hot spots" then savings of up to 40 per cent could be achieved. (A)

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