HSRs are a complex system not only in terms of technical specifications, but also with respect to operations and maintenance over the track structure. Also, track structure is basically considered as the most important and costly railway asset. Its maintenance is vital to assure safety and operating practices are also of great importance to assure that a good level of service is provided. Considering track maintenance considerations over a new HSR line, one important and critical feature is the operational regime and the question of whether the line will be operated as mixed (passenger and freight) or dedicated only to passenger traffic. This can influence the maintenance patterns: preventive maintenance planning, maintenances scheduling and assignment issues. This will be different for the dedicated and mixed HSR traffic scenarios. In this research, the main approach is focused on the interactions between track maintenance planning and operational concerns and influences in these two scenarios. With this aim and within the current paper, a model of the preventive maintenance scheduling problem (PMSP) has been selected initially from Budai (2006) and then an upgraded revision of this model (Multi-segment assignment and scheduling of preventive maintenance problem) is introduced. Furthermore, the upgraded model of PMSP has been run over a given HSR line (Tehran-Qom HSR corridor in Iran) based on the comparison between the two scenarios of dedicated HSR and upgraded mixed HSR patterns. The main requirements, similarities and differences between these two scenarios are analyzed based on preventive maintenance scheduling and assignment requisites and interactions over the operating restrictions and considerations such as track possession patterns for maintenance activities. We conclude that decision making between these two scenarios through PMSP modeling are quite complicated and depends on the technical and operational specifications of the given HSR corridor, although some general comments on tradeoffs are possible.
Multiobjective Joint Optimization of Production Scheduling and Maintenance Planning in the Flexible Job-Shop Problem
