Punctuality prognosis with OnTime

Ensuring a high quality of service starts in early planning stages and needs powerful software tools. To asses the quality of timetables SBB ordered the implementation of the sp called "Stabilitätsmodul". It completes SBB´s software toolbox by adding a software suite for timetable stability analysis.
In order to gauge the quality of traffic achievable in a timetable or, more generally, in an operating concept, it is necessary to predict how potential delays will propagate through the railway network. Random variables are used to model the types of delays arising with the aid of distribution or density functions.

This approach enpands the possibilities of timetable quality assessment compared to other simulation software:

• it is possible to analyse timetables for entire regional or national networks instead of only a network sector. So for the first time it is possible to quantify the complex networkwide effects of timetable alterations.
• Subjecting delay propagation to analytical mapping allows dependable computations to be speedily achieved even for large networks. Unlike in Monte-Carlo simulation, where concrete realisations of the delay situation are generated for each simulation run, analytical methods directly process the distribution functions of the underlying random variables. Events that in practice lead to alterations in a delay are mapped by manipulating the distribution functions in analytical methods.
  The analytical approach makes it possible to calculate the punctuality of networkwide timetables in minutes rather than hours/days.
• The short time for the timetable simulation allows for new possibilities in the process of timetable design and timetable evaluation.

The implementation of the timetable stability tool OnTime was done by cooperation of trafIT solutions gmbh, Zurich, and VIA Consulting & Development GmbH, Aachen. It is based on proven and tested methods developed at the Institute of transport science (VIA) of RWTH Aachen University. Apart from SBB it is used by Infrabel (Belgium) and in several consulting mandates. For further information see www.ontime-rail.com