A sensitivity analysis of the road load economics problem

This report describes a project conducted in the transport planning section of the Australian Road Research Board (ARRB) in 1971-72. A computer model, which simulates the extra cost of pavement and bridge construction and the savings in haulage costs caused by a raising of axle weight limits, was written and debugged. Provision could be made for including safety costs, amenity effects and enforcement costs. The model was used to test the sensitivity of the benefit/ cost ratio of a change in axle weight limits to changes in all of the parameters thought to be significant. The parameters were tested over a range of values thought to cover most Australian roads. This analysis showed the most important variables to be the power to which axle weights are raised in calculating repetitions, pavement material costs, traffic intensity and road width, the length of defective bridges per mile of road, and the magnitude of the increase in weight limits (a).