An optimization model for freight transport using urban rail transit

In this paper, we discuss a new concept for freight transport within the borders of a city with an urban rail transit system. A rising trend in some countries, urban rail transit systems are an alternative method for freight transport through cities. In these systems, the same railway is shared between passenger trains and cargo trains. We present a decision support framework for the problem of urban freight movement by rail together with mathematical methods for the optimal distribution of goods. The problem we consider has a single rail line on which some stations can be used as loading/unloading platforms for goods. Demand is known in advance and each client desires a different time for the delivery. First, we start with the case of two stations for which an approximation algorithm and a pseudo-polynomial dynamic programming algorithm are presented. Afterwards we extend the setting to several stations and develop a heuristic method, two mixed integer models and an ϵ-constraint. We provide numerical results that demonstrate the speed at which the various methods solve different sized versions of the problem.