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Tilting trains: Enhanced benefits and strategies for less motion sickness
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Carbody tilting is today a mature and inexpensive technology that allows higher train speeds in horizontal curves, thus shortening travel time. This doctoral thesis considers several subjects important for improving the competitiveness of tilting trains compared to non-tilting ones. A technology review is provided as an introduction to tilting trains and the thesis then focuses on enhancing the benefits and strategies for less motion sickness.

A tilting train may run about 15% faster in curves than a non-tilting one but the corresponding simulated running time benefit on two Swedish lines is about 10%. The main reason for the difference is that speeds are set on other grounds than cant deficiency at straight track, stations, bridges, etc. The possibility to further enhance tilting trains’ running speed is studied under identified speed limitations due to vehicle-track interaction such as crosswind requirements at high speed curving. About 9% running time may be gained on the Stockholm–Gothenburg (457 km) mainline in Sweden if cant deficiency, top speed, and tractive performance are improved compared with existing tilting trains. Non-tilting high-speed trains are not an option on this line due to the large number of 1,000 m curves.

Tilting trains run a greater risk of causing motion sickness than non-tilting trains. Roll velocity and vertical acceleration are the two motion components that show the largest increase, but the amplitudes are lower than those used in laboratory tests that caused motion sickness. Scientists have tried to find models that can describe motion sickness based on one or more motion quantities. The vertical acceleration model shows the highest correlation to motion sickness on trains with active tilt. However, vertical acceleration has a strong correlation to several other motions, which precludes vertical acceleration being pointed out as the principal cause of motion sickness in tilting trains.

Further enhanced speeds tend to increase carbody motions even more, which may result in a higher risk of motion sickness. However, means to counteract the increased risk of motion sickness are identified in the present work that can be combined for best effect. Improved tilt control can prevent unnecessary fluctuations in motion sickness related quantities perceived by the passengers. The improved tilt control can also manage the new proposed tilt algorithms for less risk of motion sickness, which constitute one of the main achievements in the present study. Local speed restrictions are another means of avoiding increased peak levels of motion sickness when increasing the overall speed.

The improved tilt control and the proposed tilt algorithms have proven to be effective in on-track tests involving more than 100 test subjects. The new tilt algorithms gave carbody motions closer to non-tilting trains. Rather unexpectedly, however, the test case with the largest decrease in tilt gave a greater risk of motion sickness than the two test cases with less reduction in tilt. It is likely that even better results can be achieved by further optimization of the tilt algorithms; the non-linear relation between motions and motion sickness is of particular interest for further study.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , vi, 36 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2011:26
Keyword [en]
tilting trains, running time, ride comfort, motion sickness, tilt control
National Category
Vehicle Engineering
Research subject
Järnvägsgruppen - Gröna tåget
Identifiers
URN: urn:nbn:se:kth:diva-33077ISBN: 978-91-7415-948-6OAI: oai:DiVA.org:kth-33077DiVA: diva2:413225
Public defence
2011-05-19, D3, Lindstedtsvägen 5, KTH, Stockholm, 09:30 (English)
Opponent
Supervisors
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note
QC 20110429Available from: 2011-04-29 Created: 2011-04-28 Last updated: 2012-06-12Bibliographically approved
List of papers
1. Research on the competitiveness of tilting trains
Open this publication in new window or tab >>Research on the competitiveness of tilting trains
2007 (English)In: Proceedings of Railway Engineering - 2007, Edinburgh: Engineering Technics Press , 2007Conference paper (Other academic)
Abstract [en]

Research has been conducted on areas identified to have potential to further improve the competitiveness of tilting trains.

The running times improves with increased cant deficiency, top speed and tractive performance; however the benefit of increased top speed and tractive performance is small above a certain level. 15 minutes running time (9%) may be gained on the Swedish line Stockholm – Gothenburg (457 km) if cant deficiency, top speed and tractive performance are improved compared with existing tilting trains. One interesting conclusion is that a non-tilting train will, independent of top speed and tractive power, have longer running times than a tilting train with today’s maximum speed and tractive power.

Guidelines for installation of cant are given, optimizing the counteracting requirements on comfort in non-tilting trains and risk of motion sickness in tilting trains. The guideline is finally compared with the installed cant on the Stockholm – Gothenburg line.

Line design and particularly the distance between the passing possibilities are studied for different mixed traffic with high-speed tilting trains and freight trains. The necessary distance between the passing possibilities becomes short when the number of freight trains increases.

Place, publisher, year, edition, pages
Edinburgh: Engineering Technics Press, 2007
National Category
Vehicle Engineering
Research subject
Järnvägsgruppen - Gröna tåget
Identifiers
urn:nbn:se:kth:diva-33061 (URN)0-947644-61-10 (ISBN)
Conference
Railway Engineering - 2007
Note
QC 20110428Available from: 2011-04-28 Created: 2011-04-27 Last updated: 2011-05-06Bibliographically approved
2. Tilting trains: benefits and motion sickness
Open this publication in new window or tab >>Tilting trains: benefits and motion sickness
2010 (English)In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, Vol. 224, no F6, 513-522 p.Article in journal (Refereed) Published
Abstract [en]

Carbody tilting is today a mature and inexpensive technology that allows higher speeds on curves, thus shortening travel time. The technology has been accepted by many train operators, but some issues are still holding back the full potential of tilting trains. This paper focuses on improving the benefits and limiting the drawbacks of tilting trains. This is done by quantifying the possible running time benefits compared with today's tilting trains, identifying what motion components have an influence on motion sickness, and finally quantifying the influence from the increased speed on these motion components.

A running time analysis was made to show what potential there is to further improve running times by optimizing tracks and trains. Relations between cant deficiency, top speed, tractive performance, and running times are shown for a tilting train. About 9 per cent running time may be gained on the Stockholm-Gothenburg (457 km) main line in Sweden if cant deficiency, top speed, and tractive performance are improved compared with existing tilting trains. Introduction of non-tilting high-speed trains is not an option on this line due to the large number of 1000 m curves.

However, tilting trains run a greater risk of causing motion sickness than non-tilting trains. Roll velocity and vertical acceleration are the two motion components that show the largest increase, but the amplitudes are lower than those used in laboratory tests that caused motion sickness. Higher curve speeds will increase carbody motions still further, but there are some possibilities to trade between vertical and lateral carbody acceleration by increasing or decreasing roll.

Keyword
tilting trains, running time, motion sickness
National Category
Vehicle Engineering
Research subject
Järnvägsgruppen - Gröna tåget
Identifiers
urn:nbn:se:kth:diva-27046 (URN)10.1243/09544097JRRT282 (DOI)000284103500001 ()2-s2.0-78349287708 (ScopusID)
Note
QC 20101213Available from: 2010-12-13 Created: 2010-12-06 Last updated: 2011-05-06Bibliographically approved
3. Motion sickness on-track testing
Open this publication in new window or tab >>Motion sickness on-track testing
2008 (English)In: Proceedings of the 43rd UK Conference on Human Response to Vibration, 2008Conference paper (Other academic)
Abstract [en]

The present evaluation of motion sickness during on-track tests is based on data collected by the Fast And Comfortable Train (FACT) project at the Nordic field tests 2004.

The method chosen for this analysis was to use linear regression between combinations of the collected motion data during the run and the passengers reported level of nausea. The methods of these analyses are based on earlier similar analyses, but here applied on an extended set of data including: transversal accelerations, rotational accelerations, products between transversal and rotational accelerations and more.

Scientists have tried to find models that can describe motion sickness based on one or more motion quantities. The models of motion sickness are derived either by tests in laboratories or by tests on train. In mathematical statistical evaluations these models may be used as hypotheses to be tested. The present analysis is based on six different hypotheses. The model on vertical acceleration shows the highest correlation to motion sickness on trains with active tilt. It is consistent with increased levels of vertical motions in tilting trains compared with non-tilting ones.

However, correlation is high between vertical acceleration and several other motions, which excludes that vertical acceleration is pointed out as the cause to motion sickness in tilting trains. This is a known problem caused by the rules to design railways and how tilting trains acts today.

Keyword
Tilting trains, Motion sickness, On-track testing
National Category
Vehicle Engineering
Research subject
Järnvägsgruppen - Gröna tåget
Identifiers
urn:nbn:se:kth:diva-33074 (URN)
Note
QC 20110428Available from: 2011-04-28 Created: 2011-04-28 Last updated: 2011-05-06Bibliographically approved
4. Strategies for less motion sickness on tilting trains
Open this publication in new window or tab >>Strategies for less motion sickness on tilting trains
2010 (English)In: Proceedings of Comprail 2010, Southampton: WIT Press , 2010, 581-591 p.Conference paper (Other academic)
Abstract [en]

Many railways have put tilting trains into operation on lines with horizontal curves with small radii. Tilting trains have vehicle bodies that can roll inwards, reducing the lateral acceleration perceived by the passengers. Tilting trains can therefore run through curves at higher speeds. However, excessive tilt motions can cause motion sickness in sensitive passengers. On the other hand, too little tilting will cause discomfort from high lateral acceleration and jerk [1].

The present paper presents new tilt algorithms aimed at balancing the conflicting objectives of ride comfort and less motion sickness. An enhanced approach is taken, where the amount of tilt depends on the local track conditions and the train speed. The paper shows how selected tilt algorithms influence certain motion sickness related carbody motions.

Speed profiles designed to avoid local peaks in the risk of motion sickness are another possibility. The speed profiles for both tilting and non-tilting trains are today set from safety and comfort perspectives only, thus minimizing the running time. The present paper shows how speed profiles could be used to balance the conflicting objectives of running time and less risk of motion sickness. The result is derived from simulations and put in relation to today’s tilt algorithms and speed profiles on the Stockholm – Gothenburg main line in Sweden (457 km).

Place, publisher, year, edition, pages
Southampton: WIT Press, 2010
Series
, WIT Transactions on the Built Environment, ISSN 1746-4498
Keyword
tilting train, tilt algorithm, tilt strategy, passenger comfort, motion sickness, running time simulation
National Category
Vehicle Engineering
Research subject
Järnvägsgruppen - Gröna tåget
Identifiers
urn:nbn:se:kth:diva-33075 (URN)10.2495/CR100541 (DOI)000303780200054 ()2-s2.0-78649401443 (ScopusID)978-1-84564-468-0 (ISBN)
Conference
12th International Conference on Computer System Design and Operation in the Railway and other Transit Systems
Note

QC 20110428

Available from: 2011-04-28 Created: 2011-04-28 Last updated: 2012-08-24Bibliographically approved
5. On-track test of strategies for less motion sickness on tilting trains.
Open this publication in new window or tab >>On-track test of strategies for less motion sickness on tilting trains.
(English)In: Vehicle System Dynamics, ISSN 0042-3114Article in journal (Other academic) Submitted
Abstract [en]

Carbody tilting is today a mature and inexpensive technology that permits higher speeds in horizontal curves, thus shortening travel time. However, tilting trains run a greater risk of causing motion sickness than non-tilting ones. It is likely that the difference in motions between the two train types contributes to the observed difference in risk of motion sickness. Decreasing the risk of motion sickness has until now been equal to increasing the discomfort related to quasi-static lateral acceleration. But, there is a difference in time perception between discomfort caused by quasi-static quantities and motion sickness, which opens up for new solutions. One proposed strategy is to let the local track conditions influence the tilt and give each curve its own optimized tilt angle. This is made possible by new tilt algorithms, storing track data and using a positioning system to select the appropriate data. On-track tests involving more than 100 test subjects onboard a tilting train have been performed to evaluate the effectiveness of the new tilt algorithms and the different requirements on quasi-static lateral acceleration and lateral jerk. The evaluation shows that the rms values important for motion sickness can be influenced without changing the requirements on quasi-static lateral acceleration and lateral jerk. The evaluation also shows that reduced quantities related to motion sickness lead to a reduction in experienced motion sickness. However, this relation seems to be valid in a certain range as the test case with the largest decrease in tilt gave a greater risk of motion sickness than the two test cases with less reduction in tilt. This non-linear relation has also been observed by other researchers in laboratory tests.

Keyword
tilting trains, active tilt, motion sickness, ride comfort, on-track test
National Category
Vehicle Engineering
Research subject
Järnvägsgruppen - Gröna tåget
Identifiers
urn:nbn:se:kth:diva-33076 (URN)
Note
QS 2011Available from: 2011-04-28 Created: 2011-04-28 Last updated: 2011-05-06Bibliographically approved

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