Line Capacity Simulator

A simulator has been developed at I.I.T Bombay for IRISET (Indian Railways Institute of Signal Engineering and Telecommunications) to model the operational behaviour of trains in sections of Indian Railways in sufficient detail. The simulator was primarily designed to estimate the section capacity of a given long distance track segment on the railway network, under mixed traffic conditions. The tool can be used to suggest changes to time-tables, and to analyze the effect of adding scheduled trains in a section, additional investment at a local level (such as additional loop lines and platforms) and the effect of signal failure and train delays. The simulation algorithm uses priority based scheduling of trains along with the operating constraints of block occupancies and platform availability. The operating logic of railway movement and the engineering detail in train running has been captured to allow for realistic analysis. Train velocities that depend on signal aspect (that in turn depends on the status of several trains ahead of the signal) is modelled in detail.

The simulator includes the following utilities:

Train plots on a distance vs time graph, with details of individual trains and resource usage as hidden displays.
Velocity curve of trains as a graphical display
The signal aspects seen by a train during its traversal.

After the validation of all aspects of running of trains, the simulator was tried on test sections, with close to real life conditions. Initially, this was done on the Secunderabad - Kazipet section of South Central Railway, to compare the simulation results with the analysis of the railways. One of the important motivations of the study was to see if the automatic signalling option on a given section yielded significant benefits.

Subsequently, experiments are being carried out in various environments, viz., suburban traffic section on Mumbai divison of Central Railway and mixed traffic conditions on the Virar - Dahanu road section of Mumbai division of Western Railway. The former study is directed at spacing signals for achieving a desired headway (frequency of service) and the latter study is to enable preparation of temporary timetables in the presence of major maintenance works and the ensuing speed restrictions on train movement.

The simulator has also been designed to include two elements of probabilistic behaviour that real life systems possess. One is the randomness in traversal times of trains, for various operational and commercial reasons and the other is the possible failure of automatic signalling equipment. Both of these have been considered, although systematic parametric analyses of these effects is yet to be done.