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Heterogeneity Measures and Secondary Delays on a Simulated Double-Track
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. (Järnvägsgruppen)ORCID iD: 0000-0002-5192-8074
2013 (English)In: Proceedings of the 5th International Seminar on Railway Operations Modelling and Analysis, Copenhagen, Denmark, 2013, 2013Conference paper (Refereed)
Abstract [en]

The demand for transportation on railways grows for each year and many railway lines are already used close to maximum capacity. One way to increase capacity is to reduce traffic heterogeneity. Heterogeneity is introduced when train services with different speeds operate on the same line. There are many definitions of heterogeneity in literature. Good measures are important in order to be able to quantify capacity lost due to heterogeneity, and consequently how capacity can be gained by reducing it. This paper analyse some of the existing measures as well as introduces a new one, Mean Pass Coefficient (MPC). Other measures analysed are: number of speed levels (SL), speed ratio of fastest to slowest train (SR), mean difference in free running time (MDFR) as well as sum of shortest headway reciprocals (SSHR) and sum of arrival headway reciprocals (SAHR).

Two infrastructure models of double-track lines with overtaking stations spaced at different intervals are simulated. A large number of timetables are created where traffic density as well as the mix of slower and faster trains is varied. Each timetable is characterized using the different definitions of heterogeneity and the results are used in regression analyses to determine their explanatory value with respect to secondary delays created in the simulations. Results show that MPC performs best closely followed by MDFR and SR, while SL is worse when it comes to explaining secondary delays. SSHR and SAHR also show good performance. The performance of the measures increases when primary delays are high, but is unaffected by interstation distance.

Place, publisher, year, edition, pages
Keyword [en]
Railway, delay, heterogeneity, simulation, regression
National Category
Transport Systems and Logistics
URN: urn:nbn:se:kth:diva-138247OAI: diva2:680648
5th International Seminar on Railway Operations Modelling and Analysis Rail Copenhagen 2013, May 13 -15, 2013

QC 20140602

Available from: 2013-12-18 Created: 2013-12-18 Last updated: 2015-09-02Bibliographically approved
In thesis
1. Railway capacity analysis: Methods for simulation and evaluation of timetables, delays and infrastructure
Open this publication in new window or tab >>Railway capacity analysis: Methods for simulation and evaluation of timetables, delays and infrastructure
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis the symptoms and underlying behaviour of congestion on railways are analysed and discussed. As well as in many other countries, Sweden faces increasing demand for transportation. To meet this new demand, railways play an important role. Today, the capacity of the Swedish rail network is not upgraded at the pace necessary to keep up with the increase in traffic demand. The sensitivity of the railway system rises as the capacity utilisation increases. At some point maximum capacity is reached when the marginal gain of operating one extra train is lower than the costs in terms of longer travel times and increased sensitivity to delays.

Several different methodologies are employed in this thesis to analyse capacity. The first uses real data from the Swedish rail network, train operation and delays to analyse how different factors influence available capacity and train delays. Several useful key performance indicators are defined to describe capacity influencing properties of the infrastructure and the rail traffic. The rail network is divided into subsections for which the indicators have been estimated. This makes it possible to discern their different characteristics and identify potential weaknesses.

The second approach employs the railway simulation tool RailSys in extensive simulation experiments. This methodology is used to analyse the characteristics of double-track operation. Simulation of several hundred scenarios are conducted to analyse the influence of traffic density, traffic heterogeneity, primary delays and inter-station distance on secondary delays, used timetable allowance and capacity. The analysis gives an in-depth understanding of the mechanisms of railway operation on double-track lines.

A simulation model for strategic capacity evaluation, TigerSim, is developed that can be used to speed up and improve capacity planning and evaluation of future infrastructure and timetables designs on double-track railway lines. For a given infrastructure and plan of operation, the model can be used to generate and simulate a larger number of timetables. This gives two major advantages:

  • Using many timetables makes results general
  • It is possible to consider both static and dynamic properties of the timetables in the capacity analysis

The first aspect is especially useful in the evaluation of future scenarios as the timetable then often is unknown. The second is an advantage since an improvement in capacity can be measured in a combination of increased frequency of service, shorter travel time and reduced delays. The output of the model can either be used to directly determine capacity from a quality of service perspective, or used as input to cost-benefit analysis (CBA).

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. x, 67 p.
National Category
Transport Systems and Logistics
Research subject
Järnvägsgruppen - Kapacitet
urn:nbn:se:kth:diva-172916 (URN)978-91-87353-65-9 (ISBN)
Public defence
2015-09-22, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)

QC 20150902

Available from: 2015-09-02 Created: 2015-09-01 Last updated: 2015-09-02Bibliographically approved

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