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Volume 5, Number 2, January 2009, p.101
Krishna B. MisraEditor-in-Chief, International Journal of Performability Engineering
Transportation systems are lifelines of a nation. These are physical systems that are vital for the health, safety, comfort, and economic activities and prosperity of a nation. Any complete or partial impairment of these can have a major impact on economic productivity as well as making peoples' daily lives and livelihood more difficult. These are critical systems required for moving people and material to locations distributed geographically. Therefore, we decided to have International Journal of Performability Engineering (IJPE) devote its issues occasionally to the important and critical aspects of these systems. We start this task with the discussion of reliability and safety of railway systems and eventually, we will cover aviation, shipping and road transportation problems in subsequent issues of IJPE.
Railway system reliability and maintenance not only ensures safety and track performance but also can reduce the operational costs, improves equipment effectiveness, and eventually the performance of a railway infrastructure. This leads to control the loss of revenue and unexpected costs due to breakdowns and accidents. Railway industry is compelled to reduce wastages, improve quality and maximize infrastructure effectiveness. Benchmarking is commonly used as an effective tool in continuous improvement of the operations of railways. It helps in developing realistic goals, strategic targets and facilitates in achievement of excellence in operation and maintenance.
In the first paper of this issue, the author tries to develop indicators related to the availability of railway system so that the losses to the stakeholders are minimal. Most of the availability indicators are calculated based on punctuality or on capacity. The train traffic controllers work on the basis of timetable and get inputs from train drivers, infrastructure personnel and the train positioning system. The timetable establishes a trade-off between traffic and track works such as preventive maintenance. When some non-planned event occurs, the controllers can make trade-offs, utilizing different recovery strategies, such as terminating trains prior to their timetabled terminus or delaying trains in order to lower total delays.
In the second paper, the authors consider the problem of railway track degradation which is affected by the operational conditions, characteristics of bogie type, million gross tonnes (MGT), curvature, traffic type and environmental conditions. Wear and fatigue in rails are the major contributors of degradation of rails. Other factors such as grinding frequency, lubrication frequency and climatic conditions also affect the degradation. Estimation of parameters for developing failure models is required for the prediction of expected number of rail defects over a period of time in order to develope a preventive strategy.
In the third paper, the failure mode and effect analysis (FMEA) is applied to analyze the railway signalling system performance, which is very critical for ensuring safety of railways and for safe running of trains by preventing occurrence of accidents and minimizing the risk to the passengers, operating personnel, and railway infrastructure. A measure, such as Risk Priority Number (RPN) is defined, which is a product of occurrence, severity, and detection. The study concludes that point and point machine, signal, and track circuit are the critical subsystems of a railway signalling system.
In the fourth paper, the author highlights the importance of teamwork in any organization. Human performance is critical to overall performance of a system. A Team can be understood as a basic unit of an organization is expected to deliver improved performance as well as improved quality in working. The paper shows the importance of balancing the implementation and development of teamwork in organizations (that is, a "soft" issue) with the improvement of "hard" system performance. Based on a study involving more than 160 teams at Volvo Trucks in Sweden, the concept of performability is introduced to understand work teams. This concept has been applied in various organizations in Europe and can be extended to the operation of critical transportation system such as railways.
In the fourth paper, the design features and performance of an Automatic Control System (ATC) is examined. ATC is basically a system which supervises the engine and the driver. At signals, data such as permitted speed, distance to next signal, gradient and speed required etc are transmitted to engine. The data is displayed to the driver and if driver is not performing correctly ATC will take over and brake the train. The increasing level of train traffic and the spread of high-speed rail lines are demanding an increasing safety level in the ATC systems. ATC systems are based both on trackside and onboard systems and their evolution has followed the introduction of new technologies. The European Vital Computer (EVC) is the core of the onboard ATC system; it supervises the movement of the train by using the information received from the trackside systems.
In the fifth paper, the authors highlight the importance of a reliable rolling stock and infrastructure equipment in railways. This eventually plays an important role in achieving high levels of safety. Therefore, the railway industry uses strategy of improving the performance of different subsystems in order to ensure safety and reliability. In fact reliability analysis is necessary in identifying bottlenecks in the system and to identify components or subsystems of low reliability for improving their performance. This paper actually provides a case study of a passenger train company of Iran and carries out reliability analysis which is used to determine the appropriate preventive maintenance strategy.
In the sixth paper, the problem associated with the maintenance of railway track is considered. In fact, railway operations today place greater demands on the track than ever before due to emphasis on faster trains with heavier payloads. With this development, time to maintain track is becoming less and less and the quality of service has to meet increased customer expectations. This necessitates improving our understanding of track degradation mechanism. Overall tamping and renewing of ballast and track are traditionally part of maintenance scheduled on regular intervals and sometimes maintenance is performed when results on track measurement exceeds limits set. However, with focus on reducing cost, maintenance needs to be optimized. This paper presents a study which describes a model that has been developed to show the relations between the degradation and variables affecting this degradation, which can help in optimized maintenance strategy.
In the last paper of this issue, with the railway tracks becoming electrified, the problem of electromagnetic interference is presented and its importance is highlighted to prevent faults that this interference can lead to in operation, with reference to Swiss railways.
My special thanks are also due to several referees, who unhesitatingly helped us in reviewing and revising the submitted papers at short notice in order to materialize this issue and in bringing these papers to the present form.