Track switches are safety critical assets that not only provide flexibility to rail networks but also present single points of failure. Switch failures within dense-traffic passenger rail systems cause a disproportionate level of delay. Subsystem redundancy is one of a number of approaches, which can be used to ensure an appropriate safety integrity and/or operational reliability level, successfully adopted by, for example, the aeronautical and nuclear industries. This paper models the adoption of a functional redundancy approach to the functional subsystems of traditional railway track switching arrangements in order to evaluate the potential increase in the reliability and availability of switches. The paper makes three main contributions. First, 2P-Weibull failure distributions for each functional subsystem of each common category of points operating equipment are established using a timeline and iterative maximum likelihood estimation approach, based on almost 40,000 sampled failure events over 74,800 years of continuous operation. Second, these results are used as baselines in a reliability block diagram approach to model engineering fault tolerance, through subsystem redundancy, into existing switching systems. Third, the reliability block diagrams are used with a Monte-Carlo simulation approach in order to model the availability of redundantly engineered track switches over expected asset lifetimes. Results show a significant improvement in the reliability and availability of switches; unscheduled downtime reduces by an order of magnitude across all powered switch types, whilst significant increases in the whole-system reliability are demonstrated. Hence, switch designs utilising a functional redundancy approach are well worth further investigation. However, it is also established that as equipment failures are engineered out, switch reliability/availability can be seen to plateau as the dominant contributor to unreliability becomes human error.

中文翻译：

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通过分析历史故障数据和引入功能冗余的子系统来提高铁路换轨的可靠性和可用性

轨道道岔是安全关键资产，不仅为铁路网络提供灵活性，而且还存在单点故障。交通密集的客运铁路系统内的开关故障会导致不成比例的延误。子系统冗余是多种方法中的一种，可用于确保适当的安全完整性和/或运行可靠性水平，例如航空和核工业已成功采用。本文模拟了对传统铁路道岔布置的功能子系统采用功能冗余方法，以评估道岔可靠性和可用性的潜在增加。该论文做出了三个主要贡献。第一的，使用时间线和迭代最大似然估计方法，基于 74,800 年连续运行中的近 40,000 个采样故障事件，为每个常见的点操作设备类别的每个功能子系统建立 2P-Weibull 故障分布。其次，这些结果被用作可靠性框图方法中的基线，通过子系统冗余将工程容错建模到现有交换系统中。第三，可靠性框图与蒙特卡洛模拟方法一起使用，以便对在预期资产寿命期间冗余设计的轨道开关的可用性进行建模。结果表明交换机的可靠性和可用性显着提高；在所有有源交换机类型中，计划外停机时间减少了一个数量级，同时证明了整个系统可靠性的显着提高。因此，利用功能冗余方法的交换机设计非常值得进一步研究。然而，还确定的是，随着设备故障的设计，开关可靠性/可用性可以被视为平台，因为不可靠性的主要因素变成了人为错误。