Paulo Fonseca Teixeira

Statistical modelling of railway track geometry degradation using Hierarchical Bayesian models

Abstract Railway maintenance planners require a predictive model that can assess the railway track geometry degradation. The present paper uses a Hierarchical Bayesian model as a tool to model the main two quality indicators related to railway track geometry degradation: the standard deviation of longitudinal level defects and the standard deviation of horizontal alignment defects. Hierarchical Bayesian Models (HBM) are flexible statistical models that allow specifying different spatially correlated components between consecutive track sections, namely for the deterioration rates and the initial qualities parameters. HBM are developed for both quality indicators, conducting an extensive comparison between candidate models and a sensitivity analysis on prior distributions. HBM is applied to provide an overall assessment of the degradation of railway track geometry, for the main Portuguese railway line Lisbon–Oporto.

Optimisation model to schedule railway track renewal operations: a life-cycle cost approach

Besides high initial construction costs, ballasted railway tracks also have high investment requirements, related to maintenance and renewal (M&R) works. Decision support tools for railway track components that optimise these works are increasingly gaining in importance. This paper presents an optimisation model that integrates ballast, rail and sleeper degradation models in a mixed integer linear programming model. This model links the decisions to renew these components with their condition and takes advantage of the integrated planning of renewal works to minimise the railway track life-cycle cost (LCC). The practical utility of the model is illustrated with a case study involving the Portuguese Lisbon–Porto line. The results indicate a reduction in track renewal cost if the grouping of components, track segments and time interval for renewal operations are optimised. Furthermore, this paper demonstrates that possible annual budget restrictions for railway track M&R operations can have an important influence on the railway track LCC.

Availability Approach to Optimizing Railway Track Renewal Operations

AbstractThis paper proposes a multiobjective optimization approach for planning railway ballast, rail, and sleeper renewal operations. The objective is to support an informed decision that considers not only the railway track life-cycle cost (LCC) but also the track occupation times required to perform interventions. Two objective functions were minimized, as follows: (1)xa0railway track unavailability caused by railway track maintenance and renewal operations, and (2)xa0railway track components’ LCC. Furthermore, to rationalize the renewal strategy, the model considers a multicomponent formulation that assesses, in time and space, the opportunistic combination of railway track renewal activities. A numerical application of the model on a real case study (Lisbon-Oporto line) is developed and discussed. The results show the interest of using this simple multiobjective optimization approach to obtain a decision-making process to support the scheduling of major railway track renewal works with an informed LCC-un...

Hierarchical Bayesian modelling of rail track geometry degradation

This paper explores hierarchical Bayesian models that can be used to predict rail track geometry degradation and thus guide planning maintenance and renewal actions. Hierarchical Bayesian models allow great flexibility in their specification, especially if they are combined with conditional autoregressive terms that can take into account spatial dependencies between model parameters. For rail track geometry degradation, conditional autoregressive terms are specified to tackle spatial interactions between consecutive rail track sections in rail track lines. An analysis of inspection, operation and maintenance data from the main Portuguese line (Lisbon–Oporto) motivates and illustrates the proposed predictive models. Inference is then conducted based on Markov Chain Monte Carlo (MCMC) simulation, which is proposed for fitting different model specifications. Finally, model comparison and a sensitivity analysis on prior distribution parameters are assessed.

Heuristic Analysis of the Effective Range of a Track Tamping Machine

This paper develops a methodology to define the optimum length of railway track that would undergo maintenance work by one tamping machine. The acquisition and logistic costs associated with the use of this type of machine are very relevant in the context of track maintenance. However, no systematic approach was found in the literature that could help managers recognize the machines’ real capacity, which seems to be more conditioned by the track’s availability for maintenance than by the machine’s performance. The methodology presented in this paper takes into account the execution capacity of the machine in a scenario in which the intervention schedule is optimized from a long-term perspective. It employs a metaheuristic process (simulated annealing) to deliver an optimized intervention schedule and the model is applied to several track length configurations. A trade-off approach is therefore adopted, confronting the minimum logistic costs with the fixed costs of the machine. The implementation of the algorithm showed significant cost reduction. However, the results of the model showed a deviation of the minimum cost solution from the quality standards. Further research could provide more insight into quality standards through its integration into a multiobjective analysis.

Life cycle cost optimisation in highway concrete bridges management

This study presents a life cycle cost prediction and cost minimisation methodology for a set of highway concrete bridges, during a medium or a long period of time, in order to facilitate the decision process of the structure management. This methodology takes into consideration bridge intervention costs in addition with some Markov matrices degradation model. It applies a genetic algorithm in order to identify the optimised intervention plan, considering the available budget and the desired minimum performance level. Some Portuguese direct and indirect cost parameters, associated with different types of interventions during bridges lifetime, are presented. Finally, a probabilistic sensitivity analysis is carried out using Monte Carlo simulations.

Incorporating Economic Assessment into Capacity Allocation and Infrastructure Charging Policies for Vertically-Separated Railways

Capacity allocation mechanisms and infrastructure access charges in vertically separated railways generally consider only the points of view of the train operator and infrastructure manager. External and other societal costs are not considered in setting these policies and in evaluating their impact on each player. This work proposes a methodological framework for evaluating impacts of capacity allocation and infrastructure pricing policies on society by applying a set of project evaluation guidelines that is normally used for new infrastructure projects to a set of capacity allocation and pricing policies. These guidelines use a cost–benefit analysis to evaluate the project and then understand the impact on each industry player and on society. A case study of the ScanMed corridor is used, looking at a congested section over the Oresund Bridge. The case study evaluates proposed capacity allocation mechanisms that prioritize either passenger or freight traffic. The results of this evaluation show the total impact of a particular policy on each player, including society. External costs are also considered in this evaluation. This approach can be used by decision makers to make more informed decisions when setting infrastructure charging and capacity allocation policy.