Title

USING SIMULATION TO EVALUATE RAIL SLEEPER REPLACEMENT ALTERNATIVES

Document Type

Journal Article

Publication Date

2002

Subject Area

organisation - management, mode - rail

Keywords

Weibull distributions, Ties, Sleepers, Simulation, Replacement strategies, Railroad ties, Materials, Maintenance management, Cross ties, Cost benefit analysis, Computer simulation, Cash flow, Benefit cost analysis

Abstract

A simulation model developed to enable a cost-benefit analysis of sleeper-replacement strategies, using the Weibull distribution, has been updated from a previous version to include up to four different types of sleepers within the track section: steel, concrete, treated timber, and untreated timber. In addition, several changes have greatly increased the number of strategies that can be simulated. The creation of a replacement strategy has been substantially developed to include two separate components, many new frequency and policy options, and the option of continuing a completed simulation with a modified replacement strategy. The model output is designed to give adequate information to the operator to determine the best course of action to take when comparing various possible replacement strategies. The results include the track condition, with the clusters of failed sleepers, and the cost of the replacement strategy. Five distinctly different replacement strategies were simulated for 20 years on a track section with 50,000 mature sleepers. These simulations showed that the nature of the strategy can have very significant effects on the cash flow required from year to year and on the annual demand for replacement materials. Careful investigation is needed to establish compromise strategies that produce acceptable numbers and sizes of clusters of failed sleepers and sleeper life in track while not exceeding available funding and materials.