Editing Tilting train (section)

== Design ==
[[File:ICE-T Neigung.jpg|thumb|An [[ICE T]] (DB class 411) leaves a curve, showing cars tilted to different degrees]]
Aeroplanes and bicycles tilt inwards when cornering, but automobiles and trains cannot do this on their own. Vehicles with high [[centre of gravity|centres of gravity]] rounding sharp curves at high speeds may topple over. To make their turns easier, the outer edge of a roadway of a high-speed highway or outer rail of a railway may be canted (raised) upward around the curve. The combination of tilt and centrifugal force combines to produce an effective acceleration that is down through the floor, reducing or eliminating any sideways component.<ref name=simmons-biddle-486>{{harvnb|Simmons|Biddle|1997|p=486}}</ref><ref name=williams-12>{{harvnb|Williams|1985|p=10-12}}</ref>

The particular angle of tilt ("superelevation") is determined by the intended vehicle speed—higher speeds require more banking. However, with a growing desire in the 1960s and 1970s to build high-speed rail networks, a problem arose: the amount of tilt appropriate for high-speed trains would be over-tilted for lower-speed local passenger and freight trains sharing the lines.<ref name=potter-69-72>{{harvnb|Potter|1987|pp=69–72}}</ref> Japan's early [[Shinkansen|bullet train]] efforts of the 1960s avoided this problem by laying all-new lines as part of a re-gauging effort, and France's [[TGV]] followed the same pattern.<ref name="jr shinkansen">{{cite web |title=About the Shinkansen |url=https://global.jr-central.co.jp/en/company/about_shinkansen/ |url-status=live |archive-url=https://web.archive.org/web/20220705211429/https://global.jr-central.co.jp/en/company/about_shinkansen/ |archive-date=5 July 2022 |access-date=20 June 2021 |website=global.jr-central.co.jp |publisher=Central Japan Railway Company |language=en}}</ref><ref>{{cite journal |url = https://www.jstor.org/stable/40061376 |title = Building a High-Speed Society: France and the Aérotrain, 1962-1974 |first = Vincent |last = Guigueno |journal = Technology and Culture |volume = 49 |number = 1 |date = January 2008 |pages = 21–40 |publisher = The Johns Hopkins University Press |doi = 10.1353/tech.2008.0018 |jstor = 40061376 |language = en}}</ref> Other operators did not have this luxury and were generally limited to much lower speeds.

Spain's national railway [[Renfe]] took a domestic invention, the [[Talgo]], and developed it into a reliable high-speed train for a low-traffic-density railway.<ref name = "railfound hist">{{cite web |url = https://artsandculture.google.com/story/talgo-a-train-ahead-of-the-curve-fundacion-de-los-ferrocarriles-espanoles/cAVRHI2dUkr-Ig?hl=en |title = Talgo: A Train Ahead of the Curve |publisher = Spanish Railway Foundation |access-date = 23 January 2023}}</ref> [[British Rail]] invested heavily in tilting-train technology to overcome the limitations of a rail network located in space-constrained built-up areas.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/uk_news/scotland/4518282.stm |work=[[BBC News]] |title=High-speed tilting train on track |date=12 December 2005}}</ref> Italy's [[Trenitalia]] and the [[Japan National Railways]] have used tilting technology to speed express trains on conventional tracks through mountainous terrain.<ref>{{cite web |first=Michae |last=Valenti |archive-url=https://web.archive.org/web/20110604063917/http://www.memagazine.org/backissues/membersonly/june98/features/tilting/tilting.html |url=http://www.memagazine.org/backissues/membersonly/june98/features/tilting/tilting.html |archive-date=4 June 2011| title=Tilting trains shorten transit time |website=Mechanical Engineering |date=1998}}</ref>

Tilting trains are meant to help reduce the effects of [[centrifugal force]] on the human body, but they can still cause [[nausea]], a problem that was widely seen on early "passive" tilting trains that exactly balanced the outward force. The effect could be felt under maximum speed and tilt, when the combination of tilting outside view and lack of corresponding sideways force can be disconcerting to passengers, like that of a "[[Amusement ride|thrill ride]]".

More limited and slower tilt could be achieved using active, or 'forced', tilting mechanisms. In trains adopting these mechanisms tilt is initiated by computers, which 'force' train bodies to tilt at specific angles based on track information. This information could be stored on board or detected using a sensor at the front of the train or using [[Automatic train stop]] beacons. The slight delay in reacting to this information leads to a short period of sideways force while the cars react. It was found that when the cars tilt just at the beginning of the curves instead of while they are making the turns, there was no motion sickness.<ref>{{cite web |url=http://www.physorg.com/news/2011-08-motion-sickness-tilting.html |title=New study shows how to eliminate motion sickness on tilting trains |website=Icahn School of Medicine at Mount Sinai |date=4 August 2011}}</ref> Researchers have found that if the tilting motion is reduced to compensate for 80% or less of lateral apparent force, then passengers feel more secure. Also, motion sickness on tilting trains can be essentially eliminated by adjusting the timing of when the cars tilt as they enter and leave the curves.<ref>{{cite tech report |title= Review of the Advanced Passenger Train: final report by Ford and Dain Partners |date= December 1981 |url= http://discovery.nationalarchives.gov.uk/details/r/C11183015 |access-date= 9 February 2016 |archive-url= https://web.archive.org/web/20161104011058/http://discovery.nationalarchives.gov.uk/details/r/C11183015 |archive-date= 4 November 2016 |url-status= live}}</ref><ref name=flop>{{cite journal |first=Mick |last=Hammer |title=The high-speed flop |journal=New Scientist |date=1 August 1985 |page=46 |url=https://books.google.com/books?id=_4SXKOBgJ_kC&pg=PA46 |access-date=8 February 2016 |archive-url=https://web.archive.org/web/20161103220415/https://books.google.ca/books?id=_4SXKOBgJ_kC&pg=PA46 |archive-date=3 November 2016 |url-status=live}}</ref>

A similar technology widely adopted across Asia and Oceania, known as ''controlled passive tilt'', achieves a similar effect by using on-board computers to limit tilt, initiated using inertia (as in traditional passive tilt).<ref name=":0" /> [[Automatic train stop]] beacons are used to inform computers of the precise location of these trains and limit natural tilt to angles specified by track data.

=== {{anchor|HighSpeed}} High-speed trains ===

{{see also|High-speed rail}}

[[File:Shinkansen N700 z15.jpg|thumb|The JR N700 Series Shinkansen, the first tilting train on Japan's high speed network]]

A ''high-speed tilting train'' is a tilting train that operates at high speed, typically defined as by the [[European Union]] to include {{convert|200|km/h|mph|0|abbr=on}} for upgraded track and {{convert|250|km/h|mph|0|abbr=on}} or faster for new track.<ref name="GeneralDefinition-EU">{{cite web |publisher=[[International Union of Railways]] |url=http://www.uic.org/spip.php?article971 |title=General definitions of highspeed |access-date=13 May 2009}}</ref>

Tilting trains operating at {{convert|200|km/h|mph|0|abbr=on}} or more on upgraded track include the [[Acela]] in the US,<ref>{{cite news |url = https://www.washingtonpost.com/transportation/2021/06/03/amtrak-acela-new-trains/ |title = Debut of Amtrak's new Acela trains delayed a year by new round of testing |newspaper = [[The Washington Post]] |last=Lazo |first=Luz |publication-place=[[Washington, D.C.|Washington]] |date = 3 June 2021}}</ref> the [[X 2000]] in Sweden,<ref>{{citation |title=The X2 Tilt Train |last=Beckhaus |first=John |work=[[Australian Railway History|Australian Railway Historical Society Bulletin]] |date=January 1995 |pages=15–17}}</ref> the [[British Rail Class 390|Pendolinos]] and [[British Rail Class 221|Super Voyagers]] in the United Kingdom,<ref name = "samath"/><ref>{{cite web |url = http://www.therailwaycentre.com/New%20DMU%20Tech%20Data%20/DMU_220_221.html |archive-url = https://web.archive.org/web/20071027164919/http://www.therailwaycentre.com/New%20DMU%20Tech%20Data%20/DMU_220_221.html |url-status = usurped |archive-date = 27 October 2007 |title = Class 221 data |date = 2 June 2008 |publisher = The Railway Centre}}</ref> and the [[ICE TD]] in Germany (the latter two being diesel powered).<ref name="HGZICTD">{{cite web |url=http://www.hochgeschwindigkeitszuege.com/germany/index_ice_td.htm |title=ICE-TD |publisher=hochgeschwindigkeitszuege.com |language=de |access-date=19 January 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090119082505/http://hochgeschwindigkeitszuege.com/germany/index_ice_td.htm |archive-date=19 January 2009 }}</ref>

Some older high-speed lines were built for lower line speeds (≤&nbsp;{{convert|230|km/h|0|abbr=on}}); newer tilting trainsets can maintain higher speeds on them.  For example, the Japanese [[N700 Series Shinkansen]] may tilt up to one degree on the [[Tōkaidō Shinkansen]], allowing the trains to maintain {{convert|270|km/h|0|abbr=on}} even on {{convert|2500|m|ft|abbr=on}} radius curves that previously had a maximum speed of {{convert|255|km/h|0|abbr=on}}.<ref>[[Japan Railfan Magazine]], December 2008. issue: "山陽・九州新幹線直通用車両 量産先行車", pp. 64-67.</ref><ref name="railfan556">{{cite magazine |title = N700系量産車|trans-title=N700 series production trains |magazine=[[Japan Railfan Magazine]] |issue = 556 |pages =13–20 |publisher = Koyusha Co., Ltd. |location = Japan |language= ja |date = August 2007}}</ref>

Many high-speed trainsets are designed to operate on purpose-built high-speed lines and then continue their journeys on legacy lines, upgraded or not. Where the legacy lines justify it, a tilting train may operate at higher speeds on the latter, even if below the normal {{convert|200|km/h|mph|0|abbr=on}} threshold, whilst operating at {{convert|250|km/h|mph|0|abbr=on}} or faster, usually with tilt disabled, on the high speed lines.