Strategies to Optimize the Deployment of Roadway Maintenance Machines for Overnight Maintenance in Urban Rail Systems

Abstract

This research investigates the effectiveness of several strategies to deploy roadway maintenance machines (RMMs) in preparation for overnight maintenance in rapid transit systems. Owing to the short windows of time available for maintenance activities in the overnight period (i.e., when revenue service is suspended), efficient deployment of RMMs is an important aspect of ensuring adequate productive time for crews at work locations. Four deployment strategies are investigated: optimizing the long-term yard storage locations of RMMs; optimizing the assignment of RMMs to work zones; optimizing the use of nonrevenue locations within the network to “preposition” RMMs closer to their work zones; and optimizing the routing and scheduling of RMMs through the network to reach the work zones. The strategies have been tested using data from the Washington Metropolitan Area Transit Authority. The results indicated that the proposed strategies reduced the time needed for RMM deployment. In the case of prepositioning, the median prepositioned RMM was deployed 23 min earlier than in the baseline (i.e., routing and scheduling alone) scenario, and the median RMM receiving a new yard storage location was deployed 16 min earlier. This was achieved without widespread negative impacts to RMMs that could not benefit from the proposed strategies for operational reasons. The results also demonstrated the potential of the routing and scheduling model as a tool to evaluate the deployment time impacts of distance-minimizing strategies, considering factors such as conflicts between RMMs and the availability of tracks to avoid disruptions to revenue service.