Integrating dynamic signalling commands under fixed-block signalling systems into train dispatching optimization models

Reference:
X. Luan, B. De Schutter, F. Corman, and G. Lodewijks, "Integrating dynamic signalling commands under fixed-block signalling systems into train dispatching optimization models," Proceedings of the 97th Annual Meeting of the Transportation Research Board, Washington, DC, 17 pp., Jan. 2018. Paper 18-01197.

Abstract:
In real operations, train dispatching works aim at adjusting the impacted schedule and reducing negative consequences during disruptions. As one of the most important components of the railway system, railway signals are used to guarantee the safety of train service. We study the train dispatching problem with consideration of railway signalling commands under the fixed-block signalling system. In such a system, signalling commands dynamically depend on the movement of the preceding train in the network. We clarify the impact of the signalling commands on train schedules, which has been so far neglected in the railway train dispatching literature, and then we innovatively propose a set of signalling constraints to implement the impact. The determination of the signal indicators is presented "if-then" constraints, which are further transformed into linear inequalities by applying two transformation properties. Activation of the train speed limits that result from the signalling commands are the core purpose of the signalling constraints, and this is implemented by using the signal indicators. Moreover, we formulate the Greenwave (GW) policy, which requires that trains always proceed under green signals, and we further investigate the impact of the GW policy on the results (delay). In the numerical experiments, the proposed signalling constraints are employed by a time-instant optimization model, which is a mixed-integer linear programming (MILP) model. The experimental results demonstrate the effectiveness of the proposed signalling constraints and show the impact of the signalling commands and GW policy on the train dispatching solution.