A tilting train is a train that has a mechanism enabling increased speed on regular rail tracks. As a train (or other vehicle) rounds a curve at speed, objects inside the train experience centrifugal force. This can cause packages to slide about or seated passengers to feel squashed by the outboard armrest due to its centripetal force, and standing passengers to lose their balance. Tilting trains are designed to counteract this discomfort. In a curve to the left, the train tilts to the left to compensate for the g-force push to the right, and vice versa. The train may be constructed such that inertial forces cause the tilting (passive tilt), or it may have a computer-controlled power mechanism (active tilt).
The first tilting train in regular public service was the 381 series electric multiple unit train operated by Japanese National Railways (JNR), which entered revenue service from 10 July 1973 on the Shinano limited express between Nagoya and Nagano on the Chūō Main Line. This technology was not fully implemented world-wide, as the marginally increased curve speeds did not justify the extra expense and technology in many cases. The British Advanced Passenger Train (being operational from 1984 to 1985) was the first to successfully implement active tilt, enabling significantly increased speeds on tight rail curves. Active tilting is the mechanism most widely used today.
Airplanes and bicycles tilt inwards when cornering, but automobiles and trains cannot do this on their own. Vehicles with high 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.
The particular angle of tilt ("superelevation") is determined by the intended vehicle speed — higher speeds require more banking. But 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. Japan's early 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. 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. British Railways invested heavily in tilting-train technology to overcome the limitations of a rail network located in space-constrained built-up areas. Italy's Trenitalia has used tilting technology to speed trains through mountainous terrain.
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 "active" 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 "thrill ride". 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. Systems typically tilt the cars based on a sensor at the front of the train, and 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. To provide information about the upcoming curves before the front of the train reaches them, a GPS system is used.
A high-speed tilting train is a tilting train that operates at high speed, typically defined as by the European Union to include 200 km/h (124 mph) for upgraded track and 250 km/h (155 mph) or faster for new track.
Tilting trains operating at 200 km/h (124 mph) or more on upgraded track include the Acela Express in the USA, the X 2000 in Sweden, the Pendolinos and Super Voyagers on the West Coast Main Line in Great Britain, and the ICE TD in Germany (the latter two being diesel powered).
Some older high-speed lines were built for lower line speeds (≤ 230 km/h (143 mph)); 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 270 km/h (168 mph) even on 2,500 m (120 ch) radius curves that previously had a maximum speed of 255 km/h (158 mph).
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 200 km/h (124 mph) threshold, whilst operating at 250 km/h (155 mph) or faster, usually with tilt disabled, on the high speed lines.
Santa Fe Pendulum-suspension car #1100
In 1938, Pullman built for the Atchison, Topeka and Santa Fe Railway an experimental pendulum-suspension "chair" car (coach), which saw service on the San Diegan train among others. Mounted on high springs, the car tilted inwards on curves to counterbalance the cant deficiency with the induced centrifugal force. As it relied on passive components, it was not entirely successful, and the lack of damping produced a sea-sickness inducing rolling motion that doomed the experiment.
In 1956, SNCF experimented with a self-propelled pendulum car, which also relied on centrifugal force. This experiment demonstrated the need for an active suspension system to tilt the coach bodies.
The first successful European tilting train design was the Talgo in Spain, developed in the 1978s as a lightweight, fast train using passive tilt. The Spanish National Railway, RENFE, adopted the system widely, but was restricted to the Iberian peninsula initially.
The first test of a Talgo in the United States was the John Quincy Adams with Fairbanks-Morse P-12-42 tested by the New York, New Haven and Hartford Railroad in 1957–1958. Due to technical troubles and the precarious financial state of the New Haven railroad, the trainset was set aside. The first full commercial application of passive tilting trains appeared in early 1980s with the Talgo Pendular. Talgo is currently in its 21st generation of production. Talgo trains are in service in various parts of Europe, and built under licence in Latin America and Asia. In North America, Amtrak uses Talgo trains in its Cascades service in the Northwest.
The first Talgo tilting series were the "pendular" ones from 400 series onwards.
The first tilting train to enter into regular service in North America was the United Aircraft TurboTrain, used by Canadian National Railways in 1968. It should be rightfully considered the first tilting train in service in the world. It assured daily service between Montreal and Toronto at speeds of 150 km/h, until it was replaced by Bombardier LRC trains in 1982 which would increase cruising speeds to 200 km/h. United Aircraft Turbos were also used by Amtrak between Boston and New York. The UAC Turbos had a passive tilt mechanism based on a four-bar arrangement, and they inspired the second generation of TALGO trains.
In Italy, various possibilities were explored (including one early design for fixed carriages with tilting seats). A number of prototypes were built and tested, including an automotrice (self-propelled) derived from ALn 668 diesel car and provided with tilting seats. The first working prototype using a tilting carbody was ETR Y 0160, an electrically powered car launched by FIAT in 1969. This was the first to be christened Pendolino.
This design led to the construction of a whole EMU in 1975, the ETR 401, built in two units by FIAT. One was put into public service on 2 July 1976 on the Rome-Ancona (later extended to Rimini) line, operated by Italian State Railways. Between Roma and Ancona (km. 295), the train took 2 hours and 50 minutes, while the ordinary trains took 3 hours and 30 minutes. The train had four cars and was mostly considered a travelling laboratory for the new technology. The second unit was adapted for service to the wide-gauge RENFE Spanish lines.
In 1982, FIAT acquired patents for the tilting bogie used in the ill-fated British project APT. This and other improvements led to the introduction of the more advanced ETR 450, the first Pendolino to enter regular service in the world. Characterized by an 8-car (later 9-car, with the addition of a restaurant coach) configuration, ETR 450 could run the Rome-Milan line in under four hours, at speeds up to 250 km/h. Passenger numbers increased from 220,000 in 1988 to 2.2 million in 1993.
In 1993, the next generation, the ETR 460, styled by Giorgetto Giugiaro, began service. Though plagued by technical teething problems, the ETR 460 introduced several innovations, such as more powerful AC asynchronous motors. Furthermore, the pistons actuating the anti-tilting action were placed in the bogie instead of on the carbody sides: this permitted the reorganisation of the vestibules and passenger compartment areas, improving comfort. The bogie-to-body connection is extremely simple and easy to make, with clear advantages for maintenance. For safety and comfort reasons, maximum tilt was reduced to 8° from the 13° of the ETR 450.
ETR 460 keeps axle load to an extremely low level (14.5 ton/axle), to allow the train to negotiate curves up to 35% faster than conventional Intercity trains (locomotive plus coaches). The body, which exploits large aluminium extrusion technology, has substantial modularity and allows for extremely low axle weight, whilst fully respecting the highest safety standards, and allows the best exploitation of the space with different loading gauges.
ETR 460 was built in only 10 units. Improved versions include ETR 470 for the Italo-Swiss Cisalpino company and the ETR 480, used by Trenitalia under AC lines such as those in France and Switzerland. A total of 34 EMUs of the ETR 460/470/480 series were built.
The development of the Pendolino technology continued in the Italian factories of Alstom and the next generation, the New Pendolino, was delivered to Trenitalia and Cisalpino as the ETR 600 and the ETR 610 from 2006.
Italian Pendolinos and their derivatives still represent the only successful solution for active tilting ever adopted. The technology still in use today is almost the same developed by Fiat Ferroviaria in the 1960s-70s.
The English version of the Pendolino, the British Rail Class 390, is a 240 km/h (149 mph) electric tilting train operated by Richard Branson' Virgin Trains. The train is known as Class 390, and runs on the West Coast Main Line (London Euston to Manchester Piccadilly Station). It is a favorite with the nation and has good brake and tilt action. Class 390s have been running since 2001.
Advanced Passenger Train
The Advanced Passenger Train is the basis of tilting trains used today, although none are currently built in the UK. It was the pioneer of the active tilt to negotiate tight curves at higher speeds than previous passive tilting trains. After successfully developing, building and actually running in service for a year the train was scrapped.
In the 1970s and 1980s, British Rail wanted an advanced fast train to negotiate the UK's twisting and winding Victorian era rail system. Conventional trains were limited in speed due to the twisting nature of the network. British Rail deliberately commissioned two young, bright, inventive engineers with no experience in trains or railways to head the development of the project. One had worked in missiles and the other for the National Coal Board. They worked in isolation to the in-house British Rail engineering team. The reason for total outsiders to develop the trains was that they would have no preconceived rail engineering prejudices and would approach the problem with a fresh open mind. These fresh minds brought to trains methods and technology from other advanced fields. They brought science into British railways, an industry that from its quantum leap in innovative technology in the Victorian times, had progressed at a slow pace since then in comparison to other countries.
The by-passed in-house British Rail design engineers poured scorn on the project; nevertheless, the new engineers used their inventiveness to progress the project. The project engineers experimented with aluminium bodies, turbines, new suspension and bogies and active tilt to negotiate the British rail network at speed, developing the Advanced Passenger Train. The APT-E (E for experimental) was powered by gas turbines and the APT-P (P for prototype) was electric. With no tilting, the train was developed to break the British rail speed record. Tilting trains were not new and used passive tilt, however, which was uncommon and not widely implemented. The engineers decided that active tilt was the key to success to negotiate curves at much higher speeds.
The train was advanced in both name and nature. Not only did it actively tilt, it had hydro-dynamic brakes, was articulated, had lightweight bodies, and two power cars in the centre of the train. The latter was necessary because two power cars were deemed necessary for the proposed schedule, but the use of a "roof-line" to send the 25 kV supply along the train, and thus allow the power cars to be placed at the ends of the unit, was not acceptable at that time. When the prototypes were built, worked and proven the engineering development team was disbanded and the trains handed over to British Rail's in-house engineering department to build. The developing engineers moved to different fields while British Rail engineered the train into a production model. The British Rail engineers, who had little to no involvement in the development of the train, changed some of the prime and proven engineering aspects. For example, they changed the active tilt mechanism to air (pneumatic), rather than the well-developed and proven hydraulics.
The trains were introduced in 1981 yet immediately taken out of service. During initial tests some passengers complained of being nauseous due to the tilting motion. Subsequently, it was learned that this could be prevented by reducing the tilt slightly, so that there was still some sensation of cornering. The APT-P trains were quietly reintroduced into service in mid-1984 and ran regularly for a year, the teething problems having been corrected. The political and managerial will to continue the project and build in numbers the projected APT-S production vehicles, had evaporated under an in-house engineering management who felt slighted and by-passed in a project they did not develop. Despite being an eventual success, the project was scrapped by British Rail in 1985, more for political reasons than technical. This was another British innovation that was left to others to implement.
Some aspects of the technology were purchased by the Italian Pendolino group to enlarge its portfolio. Ironically, Pendolino export active tilting trains to the UK, the country that invented the active tilting train.
However, much of the technology developed for the power cars was subsequently used in the InterCity225 British Rail Class 91 locomotives, which run on the East Coast route from London to Leeds and Edinburgh.
The Economist wrote in its 21 February 1998 issue, "Tilt technology, to be sure, got off to a disastrous start in 1981. That was when British Rail (BR), Britain's old nationalised railway, had to withdraw its so-called Advanced Passenger Train after only three days of scheduled services. Passengers had complained of feeling sick, and there were many technical hitches with brakes and the state-of-the-art suspension. Since that unhappy debut, however, the technology has developed to a point where tilt trains are now being operated throughout Europe."
Light, Rapid, Comfortable
Canada's contribution is the LRC (Light, Rapid, Comfortable) train, built by Bombardier. This train is rather conventional, having separable carriages instead of articulated trailers, and can be intermingled with conventional non-tilt cars. In the United States, Amtrak experimented with the LRC in 1980, but retired it a few years later. In Canada, it entered service in 1981, and the carriages remain in use today, although the tilt mechanisms are being removed to reduce weight and maintenance costs. The LRC tilt-mechanism is power-assisted, driven by accelerometers. The ride quality is very smooth, even on relatively low-end tracks. Bombardier have since used updated versions of the LRC carriages for Amtrak's Acela Express, the third generation of tilting ICE, the new generation of fast British trains (Virgin Super Voyager) and the experimental JetTrain.
Deutsche Bahn started tests with tilting trains in Germany with its class 634 in 1967 when some class 624 DMUs were equipped with passive tilting systems. As the passengers experienced motion sickness, the tilting technology was disabled and later removed. The tests continued with the prototypes of the following class 614 units, but due to the again unsatisfying results the serial types were delivered without tilting system.
Another early train with tilting technology was Deutsche Bahn's class 403 (today this number is used by ICE 3) high speed EMU. Following its InterCity services until 1979, it was also used for airport transfers between Düsseldorf and Frankfurt (see also: AiRail Service). Class 403 was able to tilt 4°, but the fixed pantographs limited this to 2°. Shortly after the train had gone into service the tilting technology was disabled as many passengers experienced motion sickness because the pivotal point was too low.
The next attempt was made with DMUs and the well proven Italian hydraulic active tilting system. Between 1988 and 1990 DB commissioned 20 class 610 units for fast regional traffic. This time the results were quite satisfying and allowed a significant reduction of running times. Class 610 was followed by class 611 which basically was built for the same purpose (fast regional traffic with up to 160 km/h (99 mph) on twisting non-electrified lines). Class 611's tilting system was electric, with a maximum 8° tilt, based on military technology from the Leopard tank. However, after coming into service in 1996 this 50-unit class experienced problems both with the newly-developed tilting system as well as chassis and axles, so it was judged not successful. The tilting system was out of service until 2006, when hardened axles and system updates finally solved the problems. In consideration of these problems DB ordered a full re-engineering, resulting in the development of class 612. Starting in 1998, a total of 192 units were commissioned by DB. The tilting system was reliable, but when in 2004 cracks were detected in a number of wheel sets, again wheels and axles had to be replaced. Today class 612 is back to tilting operation and forms the backbone of DB's fast regional service on non-electrified lines. Additional units were sold to Croatia, where they are used for InterCity services.
Finally in 1999, DB was able to use tilting technology for its InterCityExpress services, when with class 411 and 415 an electric high-speed tilting train was commissioned. While classes 401 to 403 (without tilting technology) were to cover the newly built or modernized high speed lines at up to 300 km/h (186 mph) (class 403), classes 411 and 415 with maximum speed of 230 km/h (143 mph) were designed for older twisting main lines. A total of 60 class 411 and 11 class 415 (shorter version) have been built so far. Both classes worked reliably until late 2008 when cracks were found on an axle during a routine check. The tilting mechanism has been switched off since 23. October 2008 and the maintenance intervals were drastically reduced which lead to major service disruptions.
Much of the technical layout is derived from the ICE 3. Austria's ÖBB has purchased three units in 2007, operating them jointly with DB for services from Germany to Austria. It might be noteworthy that even though DB assigned the name ICE-T to class 411/415, the T originally did not stand for tilting but for Triebwagen (self-propelled car), as DB's marketing department at first deemed the top speed too low for assignment of the InterCityExpress brand and therefore planned to refer to this class as IC-T (InterCity-Triebwagen).
Rather luckless was class 411/415's adaptation for diesel services. In 2001 a total of 20 units were commissioned for use on the Dresden–Munich line, but these class 605 (ICE-TD) units experienced trouble from the start. After the breaking of an axle in 2002, all remaining 19 units (one fell off a working platform) were taken out of service. Even though one year later the trains were admitted to service again, DB judged their operation to be overly expensive. In 2006 those trains were used for amplifier trains and since 2008 they run on the Hamburg–Copenhagen route.
In 1998 SNCF bowed to political pressure (the tilt-train was a credible threat to the TGV dedicated high-speed line network) and put in service an experimental TGV pendulaire. Following the test programme, it was converted back to a TGV-PSE train.
Switzerland got its first tilting train ever in its territory (discounting the Cisalpino, which entered Switzerland in 1996) on May 28, 2000. The ICN (InterCity Neigezug, or InterCity Tilting Train) was made by Bombardier, including a tilting-system designed by SIG (today ALSTOM). It started service on the line from Geneva via Biel/Bienne and Zürich to St Gallen. It was a major carrier in the national exhibition Expo.02.
In Japan, tilting trains were first introduced in July 1972 in the form of 381 series EMUs on Shinano limited express services operating on the Chūō Main Line between Nagoya and Nagano. The 381 series was developed from the experimental 591 series tilting EMU built in 1969.
Many of the problems with motion sickness are related to the fact that traditional servo systems respond inappropriately to the changes in trajectory forces, and even small errors whilst not being consciously perceivable cause nausea due to their unfamiliar nature. The original Fiat ETR 401 used individual gyroscopes in each carriage so there was inevitably a lag, even though nausea had not been a major problem with this train. The APT was supposed to overcome this problem by using gyroscopes at the ends of the train and a master/slave control system which defined a "tilting curve" for the whole train. It would appear that the technology of the era was not able to implement this technique as well as required.
Modern tilting trains are profiting from state-of-the-art signal processing which senses the line ahead and is able to predict optimal control signals for the individual carriages. Complaints about nausea have by and large become a thing of the past.
Some tilting trains run on narrow gauge railways. In Japan there are many narrow gauge lines in mountainous regions, and tilting trains have been designed to run on these. In Australia the service between Brisbane and Cairns by the QR Tilt Train claims to be the fastest narrow-gauge train in the world, running at 160 km/h (99 mph).
Tilting trains around the world
Trains with tilting by inertial forces:
- Talgo XXI (Spain)
- UAC TurboTrain (United States, Canada)
- JNR 381 series (Japan), introduced in 1973 by the former Japan National Railways. Now it is used by JR West for Kuroshio, Super Kuroshio, and Yakumo.
Trains with active tilting with sensory information given by accelerometers:
- LRC designed by MLW before being bought by Bombardier (Canada)
Trains with tilting controlled by a computer:
- Acela Express (United States), a Bombardier-built high-speed tilting train operating between Boston and Washington, D.C.
- Advanced Passenger Train (United Kingdom), a British Rail project for high-speed inter-city tilting trains that saw limited service in the 1980s, from London Euston to Glasgow.
- British Rail Class 390 "Pendolino" (United Kingdom), a high-speed train run by Virgin Trains from London Euston to Liverpool/ Manchester / Glasgow / Birmingham and Wolverhampton.
- Alfa Pendular (Portugal)
- ElettroTreno (Italy)
- ICE-T, also called ICT (Germany), a tilting version of the ICE
- ICN (Switzerland), a new generation of tilting trains operated by Swiss Rail, a Bombardier-built high-speed tilting train operating between Zurich and Geneva.
- JetTrain (North America), Bombardier's experimental non-electric high-speed train
- NSB Class 73 (Norway)
- SŽ series 310 (InterCitySlovenija), a high-speed tilting train operating between Ljubljana, Maribor and Koper
- RegioSwinger (Germany and Croatia), a diesel regional tilting train. In Croatia (Croatian Railways) the train operates the premium brand services InterCity Nagibni (ICN) on the routes Zagreb–Osijek, Zagreb–Varaždin, Zagreb–Split, and Zagreb–Rijeka
- Pendolino (Italy, Finland, United Kingdom, and Czech Republic), built by Alstom (formerly Fiat); see also the British Rail Class 390.
- Virgin Train Super Voyager, a Bombardier-built high-speed tilting train operating between London and Holyhead / Wrexham / Chester and Birmingham to Edinburgh or Glasgow.
- TRA Taroko Express (Taiwan), based on JR Kyūshū 885 Series.
- Tilt Train by QR, diesel and electric tilting Traveltrains (Australia), operating between Brisbane and Cairns. Electric Tilt Train is based on the JR Shikoku 8000 series.
- X2 (Sweden), with tilting mechanism of ABB. It is also used in China under the name Xīnshísù.
- JR Shikoku 2000 series (Japan, 1989), the first tilting DMU in the world. It is used on many limited express services in Shikoku, including Ashizuri, Ishizuchi, Nanpū, Shimanto, Shiokaze, Uwakai, and Uzushio. The upgraded N2000 Series was introduced from 1995.
- JR Hokkaido KiHa 281 series (Japan, 1992), branded Heat 281 or Furico 281. It is used for Super Hokuto limited express service.
- JR Shikoku 8000 series (Japan, 1992). It is used for the limited express service on Yosan Line, namely Ishizuchi and Shiokaze.
- JR East E351 series (Japan, 1993), used for Super Azusa.
- Chizu Express HOT7000 series (Japan, 1994), used for Super Hakuto.
- JR Central 383 series (Japan, 1994), used for Wide View Shinano.
- JR Kyushu 883 series (Japan, 1994), used for Sonic.
- JR Hokkaido KiHa 283 series (Japan, 1995), branded Furico 283. It is used for limited express services Super Hokuto, Super Ōzora, and Super Tokachi.
- JR West 283 series (Japan, 1996), used for Ocean Arrow.
- JR Kyushu 885 series (Japan, 1999), used for Kamome and Sonic.
- JR West KiHa 187 series (Japan, 2001), used for Super Inaba, Super Kunibiki, and Super Oki.
Trains with active suspension:
- JR Hokkaido KiHa 201 series (Japan, 1996), used for local/rapid trains around Sapporo.
- JR Hokkaido KiHa 261 series (Japan, 1999), branded Tilt 261. It is used for Super Sōya.
- Meitetsu 1600 series (Japan, 1999), branded Panorama Super. Mainly used for Meitetsu Nishio Line limited express trains.
- Meitetsu 2000 series (Japan, 2004), branded μ-Sky. It links Nagoya and Chūbu Centrair International Airport.
- Odakyu 50000 series VSE (Japan, 2005), used for Romancecar limited express services.
- N700 Series Shinkansen (except N700-7000/8000 series) (Japan, 2007), introduced by JR Central and JR West, used for Tōkaidō and Sanyō Shinkansen lines.
- E5 Series Shinkansen (Japan, 2011), introduced by JR East, used for Tōhoku Shinkansen lines.
- E6 Series Shinkansen (Japan, 2013), introduced by JR East, used for Tōhoku Shinkansen and Akita Shinkansen lines.
- プロトタイプの世界 - Prototype World (in Japanese). Japan: Kōtsū Shimbunsha. December 2005. pp. 12–19. OCLC 170056962.
- "High-speed tilting train on track". BBC News. 12 December 2005.
- Michael Valenti, "Tilting trains shorten transit time", Mechanical Engineering, 1998
- "New study shows how to eliminate motion sickness on tilting trains ", Mount Sinai School of Medicine, 4 August 2011
- "General definitions of highspeed". International Union of Railways. Retrieved 13 May 2009.
- Das Geheimnis der Achse. In: Süddeutsche Zeitung, 22. November 2008
- Weisung für Triebfahrzeugführer der ICE-T vom 23. Oktober 2008
- Neigung zum Riss.. In: Süddeutsche Zeitung online, 26. Oktober 2008