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Analysis of capacity on double-track railway lines
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)
2010 (English)In: Transportation planning and technology (Print), ISSN 0308-1060, E-ISSN 1029-0354Article in journal (Refereed) Accepted
Abstract [en]

In Sweden rail traffic is almost never separated according to speed. On several double-track lines the mix of heavy freight, regional and high speed trains imposes severe capacity problems. In order to evaluate the capacity for different traffic mixes a combinatorial model, TVEM (Timetable Variant Evaluation Model), has been developed. In this model both the infrastructure and the timetable are modelled as variables. The traffic is divided into train patterns according to a presumed regular timetable and then systematically scheduled in different time locations. The timetable variants are evaluated with regard to: mean values of capacity that give the number of trains/h for the required mix, variance measures that show how the capacity depends on the timetable and scheduled delays that show the extension of run times imposed by overtakings.

The paper shows how the important distance between adjacent overtaking stations can be sampled from Weibull distributions. TVEM has been used to evaluate three different operational cases with mixed traffic. The analysis shows that the impact on capacity from the infrastructure increases with speed difference and frequency of operation for the passenger trains, while the importance of the infrastructure decreases when traffic is more homogeneous. The impact from the timetable is strongest when the speed differences are low and/or the frequency of passenger trains is low. Capacity loss due to increased speed differences can be compensated for with additional overtaking stations. The slower trains suffer from a considerable increase in scheduled delays when speed differences increase.

Place, publisher, year, edition, pages
2010.
Keyword [en]
Double-track, railway operation, railway capacity
Research subject
Järnvägsgruppen - Kapacitet
Identifiers
URN: urn:nbn:se:kth:diva-12723OAI: oai:DiVA.org:kth-12723DiVA: diva2:318281
Projects
Framtida infrastruktur och kvalitet i tågföring
Note
QC20100622Available from: 2010-05-07 Created: 2010-05-07 Last updated: 2017-12-12Bibliographically 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.
Series
Trita-TEC-PHD, ISSN 1653-4468 ; 10-001
Keyword
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
Identifiers
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)
Opponent
Supervisors
Projects
Framtida infrastruktur och kvalitet i tågföring
Note
QC20100622Available from: 2010-05-12 Created: 2010-05-07 Last updated: 2010-06-22Bibliographically approved

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Citation style
  • apa
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