RAILCAP
A COMPUTER TOOL FOR STUDYING CAPACITY PROBLEMS OF RAILWAY NETWORKS

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Short description

The software package RAILCAP has been developed by STRATEC with a view to reinforce its capacity to analyse problems concerning railway capacity. The chosen approach is based on a static model that is well suited for studies on railway transport planning, railway network development and capacity allotments. These will find considerable usefulness in the possibility to make fast tests of the incidence of infrastructure and operation hypotheses. Indeed, Railcap measures in a straightforward way how much of the available capacity is used by a given operation program in each characteristic stretch of a given infrastructure. It thus brings to light all bottlenecks linked to the infrastructure and almost every bottleneck linked to demand. The effect of corrective measures can quite easily be tested. Time constraints are taken into account in terms of a precise given ordering of the trains during the test period. For this reason the model is not useful for the detection of minute conflicts in the timetables of the trains. These conflicts however are generally not considered at the planning and development level and can be tackled outside the model by a direct analysis of the operating schemes of the sections concerned.

Modelling the railway network

Relying on information obtained from the network manager (mainly signalling system schemes of the lines), the modeller designs a computer model of all railway tracks situated in the perimeter under study which are being used for direct haulage of commercial transport between the junctions of the network concerned. This implies that following elements are normally but not necessarily excluded from the model(except when in a later stage the analysis shows these elements to be interesting) :

maintenance and marshalling tracks (except when they cross main lines and are used during the reference periods),

private sidings,

marshalling yards and sidings,

interconnections between lines used only in exceptional circumstances (reverse lanes, marshalling lanes, crossings to yards,...).


The data needed include in particular :

the longitudinal description of the tracks and the position of switches and crosses,

the position of the block system’s transition points (insulated joints,...),

type and position of the signals (including speed limits).


Basic element for the modelling is the network segment, delimited by a physical or functional network node (for instance a switch or a speed limit transition point) or by a block system’s transition line (for instance an insulated joint in the electric signalling system). On the other hand, the basic element for the study of capacity corresponds with the "track circuit" of the electric signalling system. It consists of one or several network segments that form an entity that, on a well-defined moment in time, is totally restricted to the exclusive use of one train (either because the train is passing it or because it is enclosed in a route that will be or is being used by the train).

The model is accordingly able to measure how much of the available capacity is used by actual or projected traffics for a large number of elementary sections. Depending on the circumstances these sections are :

track sections situated on lines or in stations,

network nodes (points, graded crossings or junctions,...),

platform tracks.


Modelling the operations programs

On the model the operating programs are codified as an accurate succession of trains characterized by :

the route they follow across the network,

the stops they make in stations,

their length,

their maximum speed,

their maximum acceleration rate.


Calculation of the operations program’s influence on the available capacity

The model computes for every elementary section, as a percentage, during how much of the available time it would be occupied by the operations program under review during the simulated period.

The software produces reports on screen and on paper (tables and thematic charts of the network) indicating the capacity used by a scenario and the differences between two scenarios.

Flexible and adaptable software

Specific parameters make it possible to adapt the model to the particularities of the analysed network. Moreover, STRATEC improves the software continuously and adapts it according to the special circumstances encountered. By doing so the software has been adapted very recently in order to deal with railway traffic running at a speed of more than 160 km/h on lines of which the block system has been designed for speeds limited to 160 km/h (Strasbourg-B>le in particular.

REFERENCES

Railcap has been used with great success in the following projects :

capacity of the station of Dijon (1999 - RFF),

capacity of the railway line Strasbourg-B>le : diagnostic and evaluation of improvements and investment programs in the face of increasing traffics (1999 - French government and Alsace Region),

capacity of the railway network in the french Lorraine Region : diagnostic and evaluation of improvements and investment programs in the face of increasing traffic (1998),

additional simulations of the eastern through rail corridor in Brussels with the rail network capacity simulator Railcap (1997 - Belgian government),

study of the capacity of the railroad network serving the eastern part of the Brussels-Region and assessment of a tunnel project in view of the capacity requirements of planned suburban train services(1994 - Belgian Government).


MACRO RAILCAP

The basic element on which Railcap works is the track circuit. This enables great detail in the analysis of bottlenecks but comes with tough requirements on the modelling side. Whenever a strategic view is wanted Railcap could prove to be too cumbersome and needlessly detailed.

For this reason, STRATEC has developed in 1999 another model that better serves strategic studies purposes. It’s basic elements are homogeneous track stretches between sidings. The modelling requires more thought and relies on more hypotheses, but simulations are much easier and faster to prepare.. The results have been counterchecked with a Railcap model and it has been shown that they could be kept consistently near and above those obtained by the more precise and accurate Railcap modelling.

This MACRO RAILCAP model has been successfully applied in the framework of the TGV Rhin-Rh?ne project, to the study of the long term planning (2010- 2020 ) of the railway network in the Sa?ne-valley (between Dijon and Lyon) that already caters for one the heaviest rail traffics in Europe and will be the fastest growing rail transportation branch in France in the future. The model covers more than 1000 km of tracks (1999-2000 RFF).