A tilting train is a train with a tilting mechanism that enables increased speed on regular railway tracks. As any vehicle rounds a curve at speed, objects inside the train are in a non inertial frame and experience centrifugal force since the vehicle is rotating around the turn. This can cause packages to slide about, or a seated passenger 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. Two types of this category of trains is the Italian Pendolino and the Spanish Talgo.
In tilting trains the passenger compartment can be tilted sideways. In a curve to the left, it tilts to the left to compensate for the g-force push to the right, and vice versa.
Aeroplanes and bicycles simply tilt in place but automobiles and trains cannot do this on their own. To make their turns easier, the roadway of a high-speed highway or railway is canted inward around the curve. To a passenger in such a vehicle, the tilt makes the overall acceleration vector act downwards, rather than pushing them to the side, minimising discomfort. Vehicles with high centers of gravity rounding sharp curves at high speeds may topple over, and banking helps counteract this risk.
Other countries, with less land, weaker governmental planning powers, and more hilly terrain, were unable to follow. Specifically, 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 (the UK state railway) invested heavily in tilting train technology to overcome the limitations of a rail network in built-up areas designed for low speeds; and Italy's Trenitalia has invested heavily in tilting technology to speed trains through Italy's mountainous terrain.
Even though tilting trains are meant to help reduce the effects of centrifugal force on the human body, tilting trains can still cause nausea as they do not reduce the Coriolis effect on balancing systems. 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 force passengers feel more secure.
The first successful European tilting train designs were the Talgo in Spain, developed in the 1950s 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 trainset 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 in North America appeared in early 1970s, with the United Aircraft TurboTrain, an adaptation of the second generation of the TALGO. The TALGO is still in production in its 21st generation. 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 trainsets in its Cascades service in the US Northwest, having earlier experimented with them in the Northeast Corridor.
The first tilting train to enter into regular service in North America was the United Aircraft TurboTrain, used by Canadian National Railways, in 1969. Plagued with frequent breakdowns of its turbine power plants, it nevertheless assured daily service between Montreal and Toronto until it was retired in 1984, having been replaced by Bombardier LRC trains. United Aircraft Turbos were also used by Amtrak between Boston and New York in the early 1970s. The UAC Turbo had a passive tilt mechanism and they inspired the second generation of TALGO trains. Its ride quality was mediocre. Due to the inadequate suspension on the single axle trucks (bogies) between the cars, the tilt system required a direct connection between bogies and coaches. None are currently in use.
In the 1970s and 1980s, following the success of its InterCity 125, British Rail built a tilting train called the Advanced Passenger Train. The APT-E (E for experimental) was powered by gas turbines and the APT-P (P for prototype) was electric. The train was advanced in both name and nature. Not only did it tilt, it had hydro-dynamic brakes, it was articulated and it had 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 25kV supply along the train (and thus allow the power cars to be placed at the ends of the consist) was not acceptable at that time. Due to all this complexity the train was never reliable enough to go into service and so the project was scrapped, although some aspects of the technology were purchased by the Pendolino group to enlarge their portfolio. During tests some passengers reported that the tilting motion made them nauseous. Subsequently it was learned that this could be prevented by reducing the tilt slightly, so that there was still some sensation of cornering.
Much of the technology developed for the power cars was subsequently used in the InterCity225 (Class 91) trains which run on the East Coast route from London to Leeds and Edinburgh.
The Economist weekly 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."
Another tilting train to enter into regular service was the Pendolino. The original ETR 401 train was built by FIAT in 1975 for the Italian State Railways following a prototype in 1970 and ran successfully for many years. The Pendolino project ticked over on a low budget developing a hypothetical successor until the early 80s when the go ahead was given to build a new fleet, which was the ETR 450. Later developments of this train (ETR 460 and ETR 480) have been very successful and are used throughout Europe. The latest development in this line is the ETR 610, which will enter service in Switzerland and Italy (and possibly Germany) in 2007/8 on the Cisalpino routes.
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. 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.
Another early train with tilting technology was Deutsche Bahn's class 403 (old - today this number is used by ICE 3) high speed EMU, which entered into service in 1973. Following it's 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 went into service, the tilting technology was disabled as many passengers again 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 on twisting not electrified line). Class 611's tilting system was electric, with a maximum 8° tilt, based on military technics from the Leopard tank. However, after coming into service 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 systems was reliable, but after 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 un-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, as with class 411 and 415 an electric high speed tilting train was commissioned. Whereas classes 401 to 403 (without tilting technology) were to cover the newly built or reconstructed high speed lines with uo to 300 km/h (class 403), classes 411 and 415 with maximum speed of 230 km/h were designed for older, twisting main lines. A total of 60 class 411 and 11 class 415 (shorter version) have been build so far. Both classes work reliable. 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 event though DB assigned the name ICE-T to class 411/415, the T originally did not stand for tilting, but for Triebwagen (railcar), 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 adoption 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 of a working platform) were grounded. Even though one year later the trains were admitted to service again, DB judged their operation the be overly expensive. Today they are used for amplifier trains. Starting end of 2007, it is planned to deploy class 605 on the Hamburg-Copenhagen route.
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 and entered service, running first from Geneva via Biel/Bienne and Zürich to St. Gallen. It was a major carrier in the national exhibition Expo.02.
In Japan, the beginning of the usual operation of the tilting train is the operation of limited express しなの (former name of Nagano) by 国鉄381系電車 electric multiple unit in Chūō-saisen (central west line) of Japanese National Railways in 1972 . 381 was mass-produced based on data of 国鉄591系電車 electric multiple unit that had been made for trial purposes in 1969. Though Japanese National Railways became the Japan Railways Group by being divided in 1987, the concept model of JR四国2000系気動車 diesel multiple unit of JR Shikoku was produced in 1989, and in 1990 it was introduced (with 2000 Series mass production cars) into limited express しおかぜ (sea breeze) and 南風 (south wind). The development of new cars (both electric and diesel) are continued, and introduction to new line districts are continued one by one. Moreover, the N700 Series electric multiple unit that becomes the first tilting train of Shinkansen is scheduled to mass-produce in 2007.
Modern tilting trains have the blessing of the latest signal processing technology which reads the line ahead and is able to anticipate a very precise control signal to the individual carriages and complaints about nausea have 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 now claims to be the fastest narrow-gauge train in the world, running at 160km/h.
Trains with tilting by inertial forces:
Trains with active tilting with sensory information given by accelerometers:
Trains with tilting controlled by a computer:
Trains with active suspension: