Online railway delay management: Hardness, simulation and computation

Abstract

Delays in a railway network are a common problem that railway companies face in their daily operations. When a train is delayed, it may either be beneficial to let a connecting train wait so that passengers in the delayed train do not miss their connection, or it may be beneficial to let the connecting train depart on time to avoid further delays. These decisions naturally depend on the global structure of the network, on the schedule, on the passenger routes and on the imposed delays. The railway delay management (RDM) problem (in a broad sense) is to decide which trains have to wait for connecting trains and which trains have to depart on time. The offline version (i.e. when all delays are known in advance) is already NP-hard for very special networks. In this paper we show that the online railway delay management (ORDM) problem is PSPACE-hard. This result justifies the need for a simulation approach to evaluate wait policies for ORDM. For this purpose we present TOPSU-RDM, a simulation platform for evaluating and comparing different heuristics for the ORDM problem with stochastic delays. Our novel approach is to separate the actual simulation and the program that implements the decision-making policy, thus enabling implementations of different heuristics to ''compete'' on the same instances and delay distributions. We also report on computational results indicating the worthiness of developing intelligent wait policies. For RDM and other logistic planning processes, it is our goal to bridge the gap between theoretical models, which are accessible to theoretical analysis, but are often too far away from practice, and the methods which are used in practice today, whose performance is almost impossible to measure.

Train delay and perceived-wait time: passengers' perspective

“…In the transportation industry, the time spent for waiting is related to service assessment (Mishalani & McCord, 2010;Vansteenwegen & Oudheusden, 2006). Train delays are often considered by passengers as an indication of poor service (Berger, Hoffmann, Lorenz, & Stiller, 2011). A long delay can negatively affect overall service evaluation and increase the severity of negative affective responses such as anger because of the uncertainty created by such delays (Taylor, 1994).…”

A review on railway delay management

“…All works in this class derive their solution heuristically. Berger et al (2011b) develop TOPSU-RDM, a simulation platform that evaluates different heuristics for the DM problem, drawing delays from underlying distribution functions. The platform combines the tasks of building a model, finding an appropriate solution algorithm and experimentally evaluating it.…”

Review of real-time vehicle schedule recovery methods in transportation services

“…Li et al (2009) showed that the VRSP is an NP-hard problem. Corman et al (2010) demonstrated that the train conflict detection and resolution (CDR), a sub-class of the TRP, is NP-complete, while Berger et al (2011b) proved that the online railway delay management (ORDM) problem is PSPACE-hard (Arora and Barak 2009). Fig.…”

“…Simulation experiments show that a real-time rescheduling system could significantly reduce the total delays even in the case where additional trains are added to the timetable. Simulation has also been used by Berger et al (2011b) in order to solve the ORDM problem, in which passengers have a fixed network route, but are allowed to adapt the choices of the trains based on delays. The major objective is to minimize the total delay of passengers.…”