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Validation of a simulation model for mixed traffic on a Swedish double-track railway line
KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301). KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group. (Tågtrafikgruppen)
2009 (English)In: Proceedings of Railway Engineering 10th International Conference and Exhibition / [ed] Ford, M.C., 2009Conference paper (Refereed)
Abstract [en]

Simulation is an appropriate method of modelling complex railway operation systems. In a simulation tool it is possible to model interactions between trains and the delay propagation that follows on conflicts. This study describes a process for calibrating/validating a simulation model set up in the commercial simulation tool RailSys.

Response Surface Methodology is applied for a simultaneously calibration of seven factors. Latin Hypercubes are used as the experimental design since they support complex response surface metamodels.

The simulation model’s ability to react accurately to different operational conditions is tested. Two different traffic mixes are modelled and the validation is performed on a significantly different delay level (magnitude of disturbance).

The results show that it is possible to calibrate the model merely by adjusting the chosen factors and that these factors can compensate for simplifications made when the model was being set up. Simulated responses (mean and standard deviation measures) were compared to the real outcome and the relative differences were 2-19%. The validation generally showed greater differences.

Place, publisher, year, edition, pages
Keyword [en]
Validation, mixed railway traffic, simulation, double-track, railway operation
Research subject
Järnvägsgruppen - Kapacitet
URN: urn:nbn:se:kth:diva-12724OAI: diva2:318283
Railway Engineering 10th International Conference and Exhibition, London
Framtida infrastruktur och kvalitet i tågföring
QC20100622Available from: 2010-05-07 Created: 2010-05-07 Last updated: 2012-02-28Bibliographically approved
In thesis
1. Railway operation analysis: Evaluation of quality, infrastructure and timetable on single and double-track lines with analytical models and simulation
Open this publication in new window or tab >>Railway operation analysis: Evaluation of quality, infrastructure and timetable on single and double-track lines with analytical models and simulation
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis shows the advantages of simple models for analysis of railway operation. It presents two tools for infrastructure and timetable planning. It shows how the infrastructure can be analysed through fictive line designs, how the timetable can be treated as a variable and how delays can be used as performance measures. The thesis also gives examples of analyses of complex traffic situations through simulation experiments.

Infrastructure configuration, timetable design and delays play important roles in the competitiveness of railway transportation. This is especially true on single-track lines where the run times and other timetable related parameters are severely restricted by crossings (train meetings). The first half of this thesis focuses on the crossing time, i.e. the time loss that occurs in crossing situations. A simplified analytical model, SAMFOST, has been developed to calculate the crossing time as a function of infrastructure configuration, vehicle properties, timetable and delays for two crossing trains. Three measures of timetable flexibility are proposed and they can be used to evaluate how infrastructure configuration, vehicle properties, punctuality etc affect possibilities to alter the timetable.

Double-track lines operated with mixed traffic show properties similar to those of single-tracks. In this case overtakings imply scheduled delays as well as risk of delay propagation. Two different methods are applied for analysis of double-tracks: a combinatorial, mathematical model (TVEM) and simulation experiments.

TVEM, Timetable Variant Evaluation Model, is a generic model that systematically generates and evaluates timetable variants. This method is especially useful for mixed traffic operation where the impact of the timetable is considerable. TVEM may also be used for evaluation of different infrastructure designs. Analyses performed in TVEM show that the impact on capacity from the infrastructure increases with speed differences and frequency of service for the passenger trains, whereas the impact of the timetable is strongest when the speed differences are low and/or the frequency of passenger services is low.

Simulation experiments were performed to take delays and perturbations into account. A simulation model was set up in the micro simulation tool RailSys and calibrated against real operational data. The calibrated model was used for multi-factor analysis through experiments where infrastructure, timetable and perturbation factors were varied according to an experimental design and evaluated through response surface methods. The additional delay was used as response variable. Timetable factors, such as frequency of high-speed services and freight train speed, turned out to be of great importance for the additional delay, whereas some of the perturbation factors, i.e. entry delays, only showed a minor impact. The infrastructure factor, distance between overtaking stations, showed complex relationships with several interactions, principally with timetable factors.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 53 p.
Trita-TEC-PHD, ISSN 1653-4468 ; 10-001
Railway operation, Railway capacity, Single-track, Double-track, Partial double-track, Inter-station distance, Delay, Delay propagation, Crossing, Overtaking, Timetable flexibility, Simulation, Experimental design
National Category
Civil Engineering
urn:nbn:se:kth:diva-12727 (URN)978-91-85539-50-5 (ISBN)
Public defence
2010-05-28, E1, Lindstedtsvägen 3, KTH, Stockholm, 10:00 (English)
Framtida infrastruktur och kvalitet i tågföring
QC20100622Available from: 2010-05-12 Created: 2010-05-07 Last updated: 2010-06-22Bibliographically approved

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