Tilting train
A tilting train is a train with a tilting mechanism that enables increased speed on regular railroad tracks.
Introduction
As any vehicle rounds a curve at speed, independent objects inside it experience so-called centrifugal force since their inherent momentum forward no longer lies along the line of the vehicle's course. This can cause packages to slide about on the floor, people seated in chairs to feel squashed against their outboard armrest, and standing passengers to lose their balance.
Aeroplanes and bicycles simply tilt in place; but automobiles and railway 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 outward centrifugal force is countered by an inward gravitational one, thus removing the discomfort. (It should be noted that vehicles with high centers of gravity rounding very sharp curves at very high speeds may in fact topple over altogether; banking would also be the answer to counteract this threat. However, since passenger comfort becomes an issue at much lower speeds and gentler curves, railway designers, having kept their passengers comfortable, do not need to worry about trains overturning.)
The particular angle of tilt ("superelevation") is determined by the speed at which it is intended that vehicles will pass — faster 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 the new high-speed trains would be unacceptably over-tilted for slower-speed local passenger or freight trains which must share the lines. France, building its TGV, avoided the problem by building a special new rail network for the high-speed trains which minimized curves, likewise Japan's bullet train and many other high speed lines have necessited new infrastructure.
Other countries, with less elbow room, weaker governmental planning powers, and more hilly terrain, were unable to follow. Specificaly, The UK state railways invested heavily in tilting train technology to overcome the limitations of a rail network contructed through heavily built up areas very early on in railway history when running speeds were very slow. Italian State railways has been another heavy investor in tilting technology for thier mountain ridden country.
Tilting trains
Tilting trains are trains the upper part of which, where the passengers are seated, can be tilted sideways. In a curve to the left, it tilts to the left to compensate for the centrifugal push to the right, and conversely.
The train may be constructed such that inertial forces themselves cause the tilting, or it may be actively induced by a computer-controlled mechanism.
In the 1970s and 80s, following the success of its InterCity 125, British Rail built a tilting train called the Advanced Passenger Train. British Rail was never able to make the train reliable enough to go into service and so the project was scrapped. During tests 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.
One of the first trains with tilting technology was Deutsche Bahn's class 403, used for airport transfers between Düsseldorf and Frankfurt some decades ago (see also: AiRail Service). An attempt was made to use tilting technology to improve speeds on the extremely twisting Rhine Valley route. Shortly after the train went into service, the tilting technology was disabled as many passengers experienced motion sickness due to sudden and heavy tilting.
Some tilting trains run on narrow-gauge lines. In Japan there are many narrow-gauge lines in mountainous regions, and tilting trains have been designed to run on these. In Australia the link between Brisbane and Rockhampton, which uses tilting trains, now claims to be the fastest narrow-gauge link in the world.
Trains with tilting by inertial forces:
Trains with tilting controlled by a computer:
- ICE-T, also called ICT (Germany), tilting version of ICE
- X2 with tilting mechanism of ABB (Sweden)
- Pendolino (Italy and Britain), built by Alstom - formerly Fiat
- Pendolino (Finland)
- InterCitySlovenija - high-speed tilting train in Slovenia operating between Ljubljana, Maribor and Koper.
- Acela - American high-speed tilting train operating between Boston and Washington.