A Scheduling-Based Approach to Railway Capacity Estimation for Industrial Freight Junctions

This work proposes a Constraint Programming (CP)-based methodology for estimating the maximum freight capacity of railway junctions serving industrial areas with multiple terminals, where minimum per-destination service frequencies must be guaranteed as hard constraints to preserve commercial competitiveness among terminal operators. The problem is formulated as a scheduling problem with optional interval variables: the solver decides which candidate services to execute and when, maximising completed round-trips within a 24-hour horizon while satisfying track-occupancy exclusivity, turnout conflicts, buffer-capacity limits, a mandatory maintenance window, and a fixed passenger timetable. The approach is implemented in OptalCP and evaluated on five scenarios covering the current and a planned upgraded infrastructure of the Port of Trieste, Italy. Satisfiability queries are answered in under 13 seconds; maximisation queries establish that the as-is network sustains at least 35 freight services per day against the 11 currently operated, rising to at least 38 after the planned upgrade, with both authority service targets confirmed feasible on their respective infrastructures.