Reliability and heterogeneity of railway services

Reliability is one of the key factors in transportation, both for passengers and for cargo. This paper examines reliability in public railway systems. Reliability of railway services is a complex matter, since there are many causes for disruptions and at least as many causes for delays to spread around in space and time. One way to increase the reliability is to reduce the propagation of delays due to the interdependencies between trains. In this paper we attempt to decrease these interdependencies by reducing the running time differences per track section, i.e. by creating more homogeneous timetables. Because of the complexity of railway systems, we use network wide simulation for the analysis of the alternative timetables. We report on both theoretical and practical cases. Besides a comparison of different timetables, also general timetabling principles are deduced.heterogeneity;simulation;reliability;transportation;railways

Operations research in passenger railway transportation

In this paper, we give an overview of state-of-the-art OperationsResearch models and techniques used in passenger railwaytransportation. For each planning phase (strategic, tactical andoperational), we describe the planning problems arising there anddiscuss some models and algorithms to solve them. We do not onlyconsider classical, well-known topics such as timetabling, rollingstock scheduling and crew scheduling, but we also discuss somerecently developed topics as shunting and reliability oftimetables.Finally, we focus on several practical aspects for each of theseproblems at the largest Dutch railway operator, NS Reizigers.passenger railway transportation;operation research;planning problems

Macroeconomic resilience in a DSGE model

We use the dynamic stochastic general equilibrium (DSGE) model of Altig et al. (2005) to analyse the resilience of an economy in the face of external shocks. The term resilience refers to the ability of an economy to prosper in the face of shocks. The Altig et al. model was chosen because it combined both demand and supply shocks and because various market rigidities/imperfections, which have the potential to affect resilience, are modelled. We consider the level of expected discounted utility to be the relevant measure of resilience. The effect of market rigidities, eg. wage and price stickiness, on the expected level of utility is minimal. The effect on utility is especially small when compared to the effect of market competition, because the latter has a direct effect on the level of output. This conclusion holds for the family of constant-relative-risk-aversion-over-consumption utility functions. A similar conclusion was drawn by Lucas (1987) regarding the costs of business cycles. We refer to the literature that followed Lucas for ideas for how a DSGE model might be adjusted to give a more meaningful analysis of resilience. We conclude that the Altig et al. DSGE model does not produce a relationship between rigidities and the level of output and, hence, does not capture the effect of inflexibility on utility that one observes colloquially.