Decomposition-Based Integer Programming for Coordinated Train Rerouting and Rescheduling (original) (raw)
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2022
The railway timetables are designed in an optimal manner to maximize the capacity usage of the infrastructure concerning different objectives besides avoiding conflicts. The realtime railway traffic management problem occurs when the preplanned timetable cannot be fulfilled due to various disturbances; therefore, the trains must be rerouted, reordered, and rescheduled. Optimizing the real-time railway traffic management aims to resolve the conflicts minimizing the delay propagation or even the energy consumption. In this paper, the existing mixedinteger linear programming optimization models are extended considering a safety-relevant issue of railway traffic management, the overlaps. However, solving the resulting model can be time-consuming in complex control areas and traffic situations involving many trains. Therefore, we propose different runtime efficient multi-stage heuristic models by decomposing the original problem. The impact of the model decomposition is investigated mathematically and experimentally in different rail networks and various simulated traffic scenarios concerning the objective value and the computational demand of the optimization. Besides providing a more realistic solution for the traffic management problem, the proposed multi-stage models significantly decrease the optimization runtime.
A branch and bound algorithm for scheduling trains in a railway network
European Journal of Operational Research, 2007
The paper studies a train scheduling problem faced by railway infrastructure managers during real-time traffic control. When train operations are perturbed, a new conflict-free timetable of feasible arrival and departure times needs to be recomputed, such that the deviation from the original one is minimized. The problem can be viewed as a huge job shop scheduling problem with no-store constraints. We make use of a careful estimation of time separation among trains, and model the scheduling problem with an alternative graph formulation. We develop a branch and bound algorithm which includes implication rules enabling to speed up the computation. An experimental study, based on a bottleneck area of the Dutch rail network, shows that a truncated version of the algorithm provides proven optimal or near optimal solutions within short time limits.
Optimal multi-class rescheduling of railway traffic
Journal of Rail Transport Planning & Management, 2011
During real-time traffic management, the railway system suffers perturbations. The task of dispatchers is to monitor traffic flow and to compute feasible rescheduling solutions in case of perturbed operations. The main objective of the infrastructure manager is delay minimization, but the dispatchers also need to comply with the objectives of the train operating companies. This paper presents an innovative optimization framework in order to reschedule trains with different classes of priority, that can be computed statically or dynamically in order to include the needs of different stakeholders. An iterative train scheduling procedure is proposed in order to compute feasible train schedules for an ordered set of priority classes, from the highest one to the lowest one. At each step, the procedure focuses on the current priority class, preserving solution quality from the higher priority classes and neglecting lower priority classes in the optimization of train orders and times. The multi-class rescheduling problem is formulated via alternative graphs that are able to model precisely train movements at the microscopic level of block sections and block signals. Each step of the iterative train scheduling procedure is solved to optimality by a state-of-the-art branch and bound algorithm. The results show an interesting gap between single-class and multiclass rescheduling problems in terms of delay minimization. Each priority class is also evaluated in order to assess the performance of the different rescheduling solutions.
Reducing the time needed to solve the global rescheduling problem for railway networks
16th International IEEE Conference on Intelligent Transportation Systems (ITSC 2013), 2013
In this paper a method is introduced to reduce the computation time needed to solve the global rescheduling problem for railway networks. The railway network is modeled as a switching max-plus-linear model. This model is used to determine the constraints of the rescheduling problem. The rescheduling problem is described as a Mixed Integer Linear Programming (MILP) problem. The dispatching actions in this implementation are limited to changing the order of the trains and breaking connections at stations. These dispatching actions are most effective for smaller delays. It is therefore assumed that the delays are less than some maximum value. The proposed reduction method determines which (combinations of) control inputs will never be used if the delays are below this maximum value and removes them, as well as the constraints associated to them, resulting in a smaller model. Using the reduced model in the MILP problem significantly decreases the time needed to solve the MILP problem while still yielding the optimal solution for the original MILP problem.
Rescheduling models for networkwide railway traffic management
2012
Abstract In the last decades of railway operations research, microscopic models have been intensively studied to support traffic operators in managing their dispatching areas. However, those models result in long computation times for large and highly utilized networks. The problem of controlling country-wide traffic is still open since the coordination of local areas is hard to tackle in short time and there are multiple interdependencies between trains across the whole network.
An exact solution procedure to determine the optimal dispatching times for complex rail networks
IIE Transactions, 2006
Trains operating in densely populated metropolitan areas typically encounter complex trackage configurations. To make optimal use of the available rail capacity, some portions of the rail network may consist of single-track lines while other locations may consist of double-or triple-track lines. This paper develops a branch-and-bound procedure for determining the optimal dispatching times for trains traveling in complex rail networks. We demonstrate the efficiency of our branch-and-bound algorithm by comparing it to CPLEX, a commercially available integer program solver, on an actual rail network in Los Angeles County. meets and overtakes that minimizes train delays from the scheduled timetables while satisfying all the operational constrains. Recently, the train dispatching problem has received attention in the research community. The reason is partially due to the fact that faster trains, increasing traffic density, and the availability of real-time information on train position and velocity have made the tasks of the dispatchers too complex and demanding to perform manually. A deficient dispatching strategy may cause a decrease of the railroad line capacity and service reliability and the increase of energy consumption and pollution to the environment, or in the most severe case lead to deadlock. Therefore, building a robust methodology to handle train dispatching in an optimal way is an important research issue in rail freight transportation. In this paper, we propose a new optimization approach to dispatch trains for a general railway trackage configuration, commonly found in urban networks.
A Bilevel Rescheduling Framework for Optimal Inter-Area Train Coordination
2011
Abstract Railway dispatchers reschedule trains in real-time in order to limit the propagation of disturbances and to regulate traffic in their respective dispatching areas by minimizing the deviation from the off-line timetable. However, the decisions taken in one area may influence the quality and even the feasibility of train schedules in the other areas. Regional control centers coordinate the dispatchers' work for multiple areas in order to regulate traffic at the global level and to avoid situations of global infeasibility.
A Constraint-Based Scheduling Model for Optimal Train Dispatching
2010 Joint Rail Conference, Volume 2, 2010
Railway networks are faced to an increase demand of new services. This situation leads to train schedules close to the maximum capacity of the infrastructure. As the extension of the infrastructure is too expensive, an alternative solution is to improve traffic management in congested areas. In heavy traffic areas of rail networks, conflicts and subsequent train delays can cause considerable chain reactions during operations. A disturbance can quickly lead to many other delays called secondary delays or knock-on delays.