Advanced Passenger Train

From Academic Kids

The Advanced Passenger Train, (APT) was an unsuccessful tilting train developed by British Rail during the 1970s and early 1980s.



While Britain's East Coast Main Line from London to Edinburgh was largely straight and suited to high speed, the West Coast Main Line from London to Glasgow, and many other lines, were not straight enough to support high speeds with conventional equipment. Lateral forces would be just too high around corners; passengers would not be able to easily stand upright, and items would move on tables. Superelevation (banking of the track around curves) enabled speeds up to 100 mph, but no higher.

In order to permit a top speed of 150 mph (240 km/h), and thereby cut journey times, British Rail's engineers at Derby Works developed an advanced active tilting technology, using hydraulic rams controlled by computer to tilt the passenger cars into the curves so that no lateral forces would be felt. In 1972 the APT-E, a gas turbine-powered experimental testbed, was constructed. This was only four cars in length; two power cars, one at each end, and two 'passenger' cars full of instrumentation.

The experimental train having proved the concept, British Rail moved then to build three prototype APT-P trains. Gas turbine propulsion for trains had largely been killed off by its high fuel consumption and the increased cost of petroleum in the mid-1970s, so the new trains were electrically powered, despite thus being restricted to electrified track.

At the time, pantograph technology could not support current collection from both ends of the train at the high speeds envisaged. Therefore, the trains were designed as two half trains with twin power cars in the middle, sharing one pantograph. There was a passage through the power cars, but it was noisy, cramped and not normally permitted for passengers; therefore, each end of the train had to duplicate facilities.

Political and managerial pressure to show results led to the train being launched in 1981 when, in hindsight, it was not nearly ready for service; many technical problems persisted and reliability was not high. Predictably, the train suffered highly visible problems.

Members of the press riding the first demonstration train reported high levels of motion sickness, and this caused much bad publicity. It turned out that perfectly compensating for lateral forces around curves could induce motion sickness, since the eyes could see turning but the body didn't feel it; reducing the tilt by a few degrees so that the curves could be felt cured this.

Some cars suffered tilt failures during that first trip; furthermore, extreme cold weather caused problems, and the trains were withdrawn from service four days later. This highly visible failure was to eventually prove terminal for the project.

The trains were quietly reintroduced into service in the summer of 1982, and ran regularly, the problems having been corrected. However, the political and managerial will to continue the project and build the projected APT-S production vehicles had evaporated.

Two of the trains were scrapped, while the third was stored in a siding behind Crewe Works; it is now on display at The Railway Age, Crewe.

APT versus TGV

In stark contrast to the APT, France's high speed train, the TGV, developed around the same time, has been a great success. SNCF decided not to concentrate on the train, but on the infrastructure on which it ran. They built new Lignes Grande Vitesse (high speed lines) designed for high speed running without sharp curves and hence less the need for a complicated tilting system. Doing this in Britain would have been more problematic with public enquiries necessary and nimbyism, as shown with the initial difficulty in obtaining permission to build the Channel Tunnel Rail Link (CTRL). The French also solved the pantograph problem by having power cars at either end but collecting current only from the rear, from where it is passed along a high voltage bus line to the front power car. This bus line would have broken the UK's safety regulation.

Further uses of technology

The technology was sold to the similar Pendolino project being developed in Italy. Italian Pendolino systems incorporating original APT technology have since been sold internationally to various rail networks, including the British Class 390 Pendolino developed for the West Coast Route Modernisation. These new units were progressively introduced on the WCML from late 2003 onwards, culminating in September 2004 with the introduction of a full passenger timetable, tilt enabled from Manchester and Birmingham to London Euston.

The power unit developed was also used in the Class 91.

External links

nl:Advanced Passenger Train


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