Development of a risk-based inspection scheduling methodology for audit inspections of railroad curves on high speed main line track
Date
2016
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
This thesis presents the development of a risk based methodology to optimize the scheduling frequency and locations of audit inspection of curves on high speed rail lines performed by Federal Railroad Administration safety inspectors. In the United States, defects in the track are known to be the second leading cause of accidents and derailments and contribute to approximately 30% of all derailments per year. Only human factor caused derailments exceed this number. The approach used here is based conceptually on a risk based inspection technique developed for scheduling ultrasonic rail inspections where an inverse relationship between inspection frequency and the service defect rate was identified, i.e., as the inspection frequency increases the service defect rate in track decreases due to the finding and correcting of deficiencies in the track. Proper application of risk-based scheduling of rail testing results in increased operational safety by maintaining an acceptable level of risk (service defect rate) and quantitatively determines rail inspection frequency, based on never exceeding that level of risk. This thesis takes this overall conceptual approach and applies it to audit inspections, and developed a quantitative risk-based relationship between curve defect rates, and the audit inspection frequency for walking curved track inspections. However, it would be an unrealistic expectation to propose that audit inspections alone, would be sufficient to maintain a constant service defect rate. Railroad inspections of high speed passenger track occur at a minimum of twice per week and as such the audit inspections represent a measure of “control” to spot check the track condition. Nevertheless, it is proposed that audit walking track inspection schedules should be optimized with the goal of increasing the safety of the industry by monitoring the track condition and maintaining a defined level of risk. The increase in safety is realized by targeting the inspection scheduling locations to high-risk areas, taking into account current track conditions and developing risk-based inspection frequencies from these inputs. The result of these audit inspections include the determination of significant or widespread defects in high-risk areas, the determination of poor railroad maintenance practices and railroad compliance to the established safety standards, and increased inspection pressures in the presence of increasing risk. ☐ Similarly, risk-based track geometry inspection schedules optimize inspection location by the identification of high risk track locations in order to optimize maintenance decisions and resources while at the same time reducing the probability of a derailments at high-risk locations. The optimization of inspection location, in conjunction with inspection frequency, is critical for optimizing the overall inspection process aimed at optimized resource allocation with targeted inspection schedules. In this thesis, audit inspections apply a similar quantitative risk-based relationship with the analysis of location specific risk factors, with the goal of optimizing the audit inspection locations of walking track inspections, based on the analysis of current risk factors. The primary goal of the application of the quantitative analysis of current track conditions is a developed curve prioritization index that targets high-risk locations and determines the inspection interval to optimize the use of resources while minimizing risk. This approach allows the inspector to focus on high risk locations to reduce the risk of a train derailment at those locations.