Identifying the Input Uncertainties to Quantify When Prioritizing Railway Assets for Risk-Reducing Interventions

Natalia Papathanasiou,Bryan T Adey

doi:10.3390/civileng1020008

Abstract

Railway managers identify and prioritize assets for risk-reducing interventions. This requires the estimation of risks due to failures, as well as the estimation of costs and effects due to interventions. This, in turn, requires the estimation of values of numerous input variables. As there is uncertainty related to the initial input estimates, there is uncertainty in the output, i.e., assets to be prioritized for risk-reducing interventions. Consequently, managers are confronted with two questions: Do the uncertainties in inputs cause significant uncertainty in the output? If so, where should efforts be concentrated to quantify them? This paper discusses the identification of input uncertainties that are likely to affect railway asset prioritization for risk-reducing interventions. Once the track sections, switches and bridges of a part of the Irish railway network were prioritized using best estimates of inputs, they were again prioritized using: (1) reasonably low and high estimates, and (2) Monte Carlo sampling from skewed normal distributions, where the low and high estimates encompass the 95% confidence interval. The results show that only uncertainty in a few inputs influences the prioritization of the assets for risk-reducing interventions. Reliable prioritization of assets can be achieved by quantifying the uncertainties in these particular inputs.

Highlights

Railway managers are responsible for planning and executing risk-reducing interventions.To achieve this, they must estimate the risks due to failures as well as the costs and effects on service due to interventions for all the assets and prioritize their interventions
This paper shows how reasonably extreme estimates of inputs were used, in addition to the best estimates, to identify the input uncertainties that highly influence which assets of a railway network should be prioritized for risk-reducing interventions
To identify the assets, whose rank is sensitive to the uncertainties in the variable ‘additional travel time’, we examined first how the use of samples from skewed normal distributions for this variable affects the rank of each asset

Summary

Introduction

Railway managers are responsible for planning and executing risk-reducing interventions. To achieve this, they must estimate the risks due to failures as well as the costs and effects on service due to interventions for all the assets and prioritize their interventions . Many scholars have focused on the analysis of risk related to specific failure modes of the railway assets, e.g., [13,14,15,16,17,18,19,20,21,22,23,24,25,26,27]. Other scholars have investigated the occurrence of specific effects on the service, such as accidents (e.g., [28,29,30,31,32,33,34,35,36]), and delays (e.g., [37,38])

Methods

Results

Discussion

Conclusion