Tilting train


A tilting train is a train that has a mechanism enabling increased speed on regular rail tracks. As a train 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, and standing passengers to lose their balance. Tilting trains are designed to counteract this; by tilting the carriages towards the inside of the curve it compensates for the g-force. The train may be constructed such that inertial forces cause the tilting, or it may have a computer-controlled powered mechanism.
The first passive tilting car design was built in the US in 1937, and an improved version was built in 1939. The opening of WWII ended development. Talgo introduced a version based on their articulated bogie design in 1950s, and this concept saw use on a number of commercial services. Among these was the UAC TurboTrain, which was the first tilting train to enter commercial service in 1968 in the USA and Canada. Parallel experiments in Japan and Italy through the 591 Series and the Fiat Y 0160 developed into the highly successful 381 series which began services in 1973 and is still in service today; and the Pendolino family currently in use across 11 countries since 1976. All of these had problems with short curves like those in switchyards, where they tended to sway about. Also, because of the way the carriages always swung outward, they placed more weight on the outside of the curve, which limited their improvement in corner speed to about 20%.
Starting in the late 1960s, British Rail began experiments with their Advanced Passenger Train which pioneered the active-tilt concept. This used hydraulic rams on the bottoms of the carriages to tilt them, rotating them around their centre point rather than swinging outward. This had the advantage of keeping the carriage centred over the bogies, which reduced load on the rails, and could be turned off when navigating switches. Due to lengthy delays, the APT did not begin test runs until 1981 and entered commercial service only briefly in 1985. By this time, the Canadian LRC design had become the first active tilting train to enter full commercial service, starting with Via Rail in 1981.
Fiat developed their Pendolino design into the most successful type of tilting train, with over 500 trains active in Europe. The concept of active tilt as a whole has been independently developed by many companies. Active tilting systems are widely used today.

Design

Aeroplanes 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 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 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 and the Japan National Railways have used tilting technology to speed express trains on conventional tracks 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 "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 "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. 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.
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. 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.

High-speed trains

A high-speed tilting train is a tilting train that operates at high speed, typically defined as by the European Union to include for upgraded track and or faster for new track.
Tilting trains operating at 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.
Some older high-speed lines were built for lower line speeds ; 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 even on radius curves that previously had a maximum speed of.
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 threshold, whilst operating at or faster, usually with tilt disabled, on the high speed lines.

History

Pendulum car

The first experimental tilting train concept was the pendulum-suspension "chair" cars designed by the Pacific Railway Equipment Company. The first prototype, with an articulated bogie system, was built in 1937 and tested on the Atchison, Topeka and Santa Fe Railway that year. The company built another three pre-production models in 1939, using more conventional fore-and-aft bogies, and these saw some use with the San Diegan, among others. Mounted on high springs, the car tilted inwards on curves to counterbalance the cant deficiency with the induced centrifugal force. The opening of World War II prevented any immediate orders, and the concept was not taken up again in the post-war era.

SNCF 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.

Talgo Pendular

The Spanish Talgo company had introduced the first widely successful shared-bogie system, which allowed cars to be connected end-to-end using a single bogie instead of each car having its own bogies at either end. This design saves weight and can reduce rail wear.
In the early 1950s, RENFE experimented with passenger cars that combined the Talgo bogie with a new passive tilting system. This system used a large A-frame connected to the centre of the bogie that was as high as the cars. At the top of the A was a bearing system that the cars attached to, and a spring and damping system to smooth its motion. Because the cars were connected at this high point, they could swing to either side around the bearing axis, and this caused them to naturally pendulum outward on curves.
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 idea caught the interest of the Chesapeake and Ohio Railway, who began development of what would become the UAC TurboTrain using the same system. The TurboTrain entered service in the US and Canada in 1968.
The first successful European tilting train design was the Talgo in Spain, developed in the 1970s 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 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.

UAC TurboTrain

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 160 km/h, until it was replaced by Bombardier LRC trains in 1982. 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.

Pendolino

In Italy, the studies for a tilting train started in the mid 1960s and the concept was patented in 1967 by two engineers of Fiat railway materials, Franco di Maio and Luigi Santanera. A number of prototypes were built and tested, including an automotrice derived from ALn 668, the ALn 668 1999 diesel car, provided with tilting seats in order to test the concrete effects of active tilting technologies. 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 line, operated by Italian State Railways. Between Roma and Ancona, 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. Initially the ETR 401 was conceived as the first of a series of four trains, but the government lost interest to the project, because of financial problems, and the envelopment was temporarily interrupted, as the service in 1983 and the train was used in demonstration campaigns to foreign countries, like Germany, Switzerland, Cechoslovakia and Yugoslavia. A second unit was built for service to the wide-gauge RENFE Spanish lines, in 1977, under the nickname of Platanito. The service didn't last of long, because the problems of Spanish tracks made Platanito little useful.
New interest of the Italian government to the project in the mid 1980s, and the introduction of new technologies, led to the revise of the project of the ETR 401 with electronical systems, that led to the introduction of the slightly more advanced ETR 450, the first Pendolino to enter regular service in the world. Characterized by an 8-car configuration, and a maximum tilt reduced to 8° from the 10° of the ETR 401, for safety and comfort reasons, 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 1989, the already old technologies an concepts of some parts of the ETR 450, and the introduction of new technologies in traction, led to the development of the next generation, the result was the ETR 460, styled by Giorgetto Giugiaro, train that began service in 1996. Though plagued by technical teething problems, the ETR 460 introduced several innovations, such as more powerful AC asynchronous motors. Furthermore, the pistons actuating the 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.
ETR 460 keeps axle load to an extremely low level, to allow the train to negotiate curves up to 35% faster than conventional Intercity trains. 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, the ETR 460 France, later called as ETR 463, used by FS to the route Milan Lione, and the ETR 480, used by Trenitalia under AC-powered Italian high speed lines. A total of 34 EMUs of the ETR 460/470/480 series were built for FS.
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 most popular solution for active tilting in passenger trains. The technology still in use today is almost the same developed by Fiat Ferroviaria in the 1960s-70s.
The British version of the Pendolino, the British Rail Class 390, is a electric tilting train operated by Avanti West Coast. The train is known as Class 390, and runs on the West Coast Main Line (London Euston to Glasgow Central, Liverpool Lime Street and Manchester Piccadilly. Class 390s commenced operation in 2001 with only one being in a major derailment. Due to signalling constraints, Class 390s are limited to in regular service.

Japanese designs

Tilting trains have long been a mainstay of express services on Japan's conventional-speed, narrow gauge network. The interurban Odakyu Electric Railway began Japan's first experiments in tilting technology in the 1960s by fitting pneumatic bogies to their electric railcars, while the Japanese National Railways pioneered their form of passive-tilt technology on their experimental 591 series EMU with commercial express services on mountain lines in mind.
The first commercial tilting EMU in the world entered service as the 381 series EMUs on Shinano limited express services operating on the hilly Chūō Main Line between Nagoya and Nagano, and is still in operation on the "Yakumo" service on the Hakubi Line despite its shortcomings in ride quality and increased track wear due to its tilt mechanism that allowed up to 5° of tilt.
During the final years of the Japanese National Railways, experimentation on mechanically-regulated passive tilt - a combination known as 'controlled passive tilt', where tilt is initiated passively but controlled by computers through mechanical active suspension - culminated post-privatisation with the 2000 series DMU, built for JR Shikoku and introduced on the Shiokaze and Nanpū limited express services in 1990. With problems of ride nausea and track wear alleviated, the benefits of tilting trains on the country's mountainous Cape gauge railway system soon became apparent and since then these 'semi-active' tilting trains have seen widespread use on limited-express trains throughout the archipelago. Particularly well-known diesel and electric examples of this generation of tilting trains include JR Hokkaido's KiHa 281 series, JR East's E351 series, JR Central's 383 series, JR Shikoku's 8000 series, and JR Kyushu's 885 series.
This generation of designs has seen some popularity overseas - the 8000 series serves as the basis of the Electric Tilt Train built for Queensland Rail's Cape Gauge network. The 885 series, built as part of the Hitachi A-train family, serves as the basis of the Taiwanese TEMU1000 series tilting EMU for Taroko Express services, and some non-tilting variants including the British Rail Class 395 and British Rail Class 801.
Later developments in pneumatic active suspension - based on the DB Class 403 built decades earlier - created a generation of trains with more limited tilt but are more economical to build and easier to maintain. The experimental built in 1995 developed into the N700 series, the first revenue-earning tilting Shinkansen unit in 2007. Applications to Shinkansen lines - which would not have benefitted greatly with mechanical tilting mechanisms due to their already shallow curves that allow high speeds anyway - allowed for greater ride comfort, less track wear and slightly higher speeds leading to increased frequency. The simplicity of this technology made it possible for smaller private operators to introduce tilting trains, such as the Odakyu 50000 series VSE, a luxurious sightseeing express train with active suspension introduced not to increase speeds but to enhance ride comfort; and even cheap enough to be applied to commuter stock, such as JR Hokkaido's KiHa 201 series, which improved speeds and frequencies on Sapporo's partly non-electrified suburban railway system. This is also one of the only applications of tilting technology on 'metro-style' commuter trains to date.

German designs

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 Bundesbahn's class 403 high speed EMU. Following its InterCity services until 1979, it was also used for airport transfers between Düsseldorf and Frankfurt. 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. 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 were to cover the newly built or modernized high speed lines at up to , classes 411 and 415 with maximum speed of were designed for older twisting main lines. A total of 60 class 411 and 11 class 415 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 led 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. Even though DB assigned the name ICE-T to class 411/415, the T originally did not stand for tilting but for Triebwagen, 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.
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 units experienced trouble from the start. After the breaking of an axle in 2002, all remaining 19 units 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.

Light, Rapid, Comfortable

In 1966, a consortium of Canadian industrial firms began considering a conventionally-powered competitor to the TurboTrain, eventually emerging as the LRC in the early 1970s. This design also used an active-tilt system, but one of very different form than the ATP. The carriages rode on two C-shaped channels mounted across the top of the bogies. Tilt was accomplished by rams that pushed the bottom of the carriage side to side along these channels.
Amtrak experimented with the LRC in 1980, but retired it seven years later. In Canada, it entered service in 1981, beating the ATP into service and becoming the first operational active-tilt system. The LRC carriages remain in use today, although the tilt mechanisms are being removed to reduce weight and maintenance costs.
Bombardier has 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 and the experimental JetTrain.

Advanced Passenger Train

The Advanced Passenger Train was initially an experimental project by British Rail, with the train entering service in 1984. Although eventually abandoned, the train was the pioneer of active tilt to negotiate tight curves at higher speeds than previous passive tilting trains. For various reasons, political and technical, after running in service for a year, the train was withdrawn.
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.
The engineers at the research division, opened in 1964, had already carried out fundamental work on vehicle dynamics, with the APT to a degree an extension of this. The existing Chief Mechanical and Electrical Engineers department was overlooked by the new project, creating resentment with its engineers. The work included experimentation with aluminium bodies, turbines, suspension and bogies, and active tilt.
The APT-E was powered by gas turbines; the APT-P was electric. With no tilting, the train was developed to break the British rail speed record. Tilting trains using passive tilt were not new, but it was uncommon and not widely implemented. The engineers decided that active tilt was the key to negotiating curves at much higher speeds.
The train had hydro-dynamic brakes and lightweight articulated bodies, with two power cars in the centre of the train. 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 on to different fields while British Rail engineered the train into a production model. The BR 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, rather than the well-developed and proven hydraulics.
The trains were introduced in 1981, but almost 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. However, the political and managerial will to continue the project, by building the projected APT-S production vehicles in numbers, 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.
Much of the technology developed for the power cars was subsequently used in the non-tilting InterCity225 British Rail Class 91 locomotives, which run on the East Coast Main Line route from London to Leeds and Edinburgh.

X 2000

In 1990 Swedish railways introduced a high speed service called X 2000. The train uses an active tilting system enabling higher speeds of on standard track.

TGV Pendulaire

In 1998 SNCF bowed to political pressure and put in service an experimental TGV pendulaire. Only the passenger trailers were tilting while the two heavy power cars kept non-tilting bogies. Following the test program, it was converted back to a TGV-PSE train.

InterCity Neigezug

Switzerland got its first tilting train ever in its territory on May 28, 2000. The ICN was made by Bombardier, including a tilting-system designed by SIG. 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.

Bombardier SuperVoyager

Diesel-electric powered British Rail Class 221 serve Holyhead, Chester, Bangor and Wrexham.

Technology

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. The Electric Tilt Train also holds the record for the fastest narrow-gauge train by maximum test speed, reaching 210 km/h.

Tilting trains around the world

Trains with tilting by inertial forces :
Trains with tilting initiated by inertial forces but regulated by computer:
Trains with active tilt controlled with sensory information given by accelerometers:
Trains with tilting controlled by a computer: