ASSESSMENT OF RESIDUAL CAPACITY OF SINGLE-TRACK LINES FROM SIMULATION USING UIC 406 COMPRESSION

Abstract

How many additional trains a line can accommodate is a recurring question in timetable planning and infrastructure management. This paper presents a computational procedure that derives line-capacity indicators directly from the output of the microscopic simulator OpenTrack. The existing timetable is first adapted for import into OpenTrack; the simulator then generates, for each train, a blocking time stairway, which is converted into section occupancy intervals and compressed according to the UIC 406 method (greedy left-shifting with backward propagation and an optional overlap policy for single-track operation). From the compressed diagram, the bottleneck, infrastructure occupancy and a free-capacity indicator are determined. A residual-capacity estimate “in the tail of the day” is proposed: instead of counting gaps between existing trains, additional homogeneous paths are packed into the interval after the last compressed train, using speed profiles by official train categories. The compressed timetable is exported in an OpenTrack-compatible format for re-simulation. The procedure is demonstrated on a single-track section of main line M202 Zagreb – Rijeka in Croatia for a representative working day, quantifying the bottleneck, its utilisation and the number of additional paths by category and direction.