In this paper we estimate the impact of axle loads on rail infrastructure maintenance costs in Sweden. The results are contrasted to the cost impact of ton density, a common measure in the literature on rail infrastructure costs. We find non-linear cost elasticities with respect to a ton per axle density measure, with an estimate at the sample median that is larger than the corresponding estimate for ton density. The results are relevant for the setting of track access charges in Europe, considering that the econometric results in this paper give support to the engineering perspective - that is, axle loads are important to consider when estimating the damage caused by traffic.