Demonstration of Mechanics-Based Track Geometry Deterioration Models

The Transportation Technology Center, Inc. (TTCI) is working to build on and extend existing mechanics-based track geometry deterioration forecasting models to support improved safety and reliability of ballasted tracks. This paper demonstrates how the railway track lifecycle model (RTLM) ballast model performs against field data and makes recommendations for improvement. Overall, the demonstration showed the mechanics-based model matches the general field behavior and its variations well, and it also identified potential improvements. The field data reinforced ballast fouling index (BFI) as a key factor in track geometry degradation. Additional factors that can cause variation in the BFI-track geometry degradation relationship were also identified, along with proposed curves that are easier to fit with field data. Linear track geometry degradation, with reference to mid-chord offset measurement with tonnage, fits the field data better than a logarithmic curve, which, historically, has been used to fit settlement as a function of tonnage. Using these improvements to the model, future work will focus on making the model as flexible as possible. This means identifying and incorporating key variables, in addition to BFI, that affect track geometry deterioration and allowing the model to either give general projections in situations with little historical data or become site-specific to a particular track section by incorporating historic data.