Highway maintenance marginal costs: What if the fourth power assumption is not valid?

Highway maintenance marginal costs have been estimated in the literature using the perpetual overlay indirect approach. This approach uses the equivalent single axle load (ESAL) as the unit for traffic loading, which implies that pavement deterioration caused by an axle is proportional to the fourth power of the axle weight. This paper answers the following question: how inaccurate are maintenance marginal cost estimates when a highway agency uses ESAL? We find that the inappropriate use of ESAL does not affect the sum of maintenance marginal cost prices paid by all vehicles (at current equilibrium); however, it impacts distribution among vehicles, which reduces equity and efficiency.