MODELING DELAY RISKS ASSOCIATED WITH TRAIN SCHEDULES

Overall timetable reliability is a measure of the likely performance o f the timetable as a whole, in terms of schedule adherence. The reliab ility of arrivals is a critical performance measure for all rail marke ts. This paper presents analytically based models designed to quantify the amount of delay risk associated with each track segment, train an d the schedule as a whole. Three main types of delays are modelled, na mely: terminal/station delays; track related delays; and rolling stock related delays. The models can be used to prioritise investment proje cts designed to improve timetable reliability. For example, a comparis on can be made between track, terminal and rolling stock projects, in terms of their likely impact on timetable reliability. The effect of t imetable changes on likely reliability can also be modelled. Using the risk models developed here, it is possible to assess the likely effec t of removing/ adding sidings for passing and crossing purposes, under single line train operations. The paper illustrates the use of the mo dels using a series of tests with a timetable consisting of nine train s and six stations. The effect of changing assumptions regarding delay s due to terminal congestion; track related problems; and rolling stoc k, are modelled and the results are summarised. Also modelled is the i mpact of changes to the timetable.