This paper provides empirical evidence on the optimal timing of rail infrastructure renewal. Using an econometric approach on data from the Swedish railway network, we establish a relationship between cumulative tonnes and maintenance costs, as well as between cumulative tonnes and infrastructure failures that cause train delays. Together with average values on delay hours per failure and assumptions on passengers per train, we perform example calculations on the optimal timing for a track renewal. This timing will depend on the case considered, such as whether traffic intensity is high or low. Empirical evidence on the relationship between line capacity utilisation and delay time can provide more robust estimates for the different cases considered by an infrastructure manager. Still, the results in this paper is a significant step towards a usable cost-benefit analysis model for the timing of rail infrastructure renewals.

Cost-benefit analysis is often used in appraisal of rail infrastructure investments. A corresponding decision support is, however, not available for rail infrastructure maintenance and renewal. To for example decide whether to renew or continue to maintain an infrastructure asset, a relationship between cumulative traffic and infrastructure failures is required. This relationship is established in this paper, using an empirical (top-down) approach on Swedish data for years 2003 to 2016. It is shown that the average elasticity for track failures with respect to cumulative tonnes is 0.32, and that the elasticity varies for different levels of traffic and for different infrastructure characteristics. The results in this paper can for example be used to calculate the impact cumulative tonnes have on train delay costs, which together with a relationship between cumulative traffic and infrastructure maintenance costs are essential in an economic optimization of maintenance and renewal activities.

In this paper we estimate the impact of line capacity utilisation on the marginal cost of rail infrastructure renewals. Previous studies are mainly concerned with deterioration costs caused by traffic. This paper contributes to the literature, showing that increased line capacity utilisation can – in addition to higher deterioration costs – generate increased costs for carrying out a renewal project and/or more frequent renewals, where the latter can be motivated by efforts to curb expected delays. A top-down econometric approach is used on a Swedish dataset comprising information on renewal costs for track, electric installations, signalling, telecommunication, and other installations such as barriers, fencing and lubrication equipment. The results are relevant for rail infrastructure managers, especially in Europe where directives by the EU stipulate that track access charges are to be based on direct costs in order to contribute to an efficient use of the infrastructure.