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Crossing times on single-track railway lines: dependencies of different infrastructure and traffic factors
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)
2007 (English)In: Proceedings of Railway Engineering 9th International Conference and Exhibition / [ed] Ford, M.C., 2007Conference paper (Refereed)
Abstract [en]

Operation of single-track railway lines is characterised by crossings. Due to disturbances the crossing time is stochastic. Important properties such as capacity, run times and overall punctuality are strongly dependent on the crossing time. In non-congested situations the crossing time can be modelled analytically. SAMFOST (Simplified Analytical Model For Single Tracks) is a model that shows in a transparent way how the crossing time varies along a railway line.

This paper shows how the mean crossing time function can be used to examine timetable flexibility, i.e. possibilities to change the timetable given constraints on the mean crossing time. Three different measures for timetable flexibility are proposed, showing how the available crossing points are spread along the line and the spread of mean crossing time for available crossing points.

Many factors such as infrastructure parameters, vehicle parameters, timetable, delays etc affect the crossing time. In many cases these factors interact in complicated ways. To show this, the results of a 26-factorial experiment are presented. Partial double-tracks and passenger stops at timetable crossing points are examples of measures that give geographically local effects with strong interactions, whereas inter-station distance, vehicle type and arrival punctuality are factors with a more general impact and weaker interactions.

Place, publisher, year, edition, pages
Keyword [en]
single-track, crossing, rialway operation, delay, timetable flexibility
Research subject
Järnvägsgruppen - Kapacitet
URN: urn:nbn:se:kth:diva-12722OAI: diva2:318280
Railway Engineering 9th International Conference and Exhibition
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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