The Advanced Passenger Train (APT)

with acknowledgements to Wikipedia

The Advanced Passenger Train (APT) was a tilting high speed train developed by British Rail during the 1970s and early 1980s, for use on the West Coast Main Line (WCML). The WCML contains many curves and the APT pioneered the concept of active tilting to address these, a feature that has since appeared on designs around the world. The experimental APT-E achieved a new British railway speed record on 10 August 1975 when it hit 152.3 mile/h (245.1 km/h), only to be exceeded by the service prototype APT-P at 162.2 mile/h (261.0 km/h) in December 1979, a record that stood for 23 years.


Following nationalisation of the UK's railways in 1948, British Rail faced significant losses in passengers as the car rapidly became more popular through the 1950s and 60s. By 1970, passenger numbers were roughly half what they had been immediately before World War II. In an attempt to maintain some level of profitability, the Government commissioned a report 'The Modernisation of British Railways' which resulted in the abandonment of many lines as part of the 1963 "Beeching Axe". In spite of this significant restructuring, the company was encumbered with track and structures dating from before WW2 and with routes laid out and built by the Victorians.

BRís Research Division carried out what is considered to be the most detailed study of the dynamics of steel wheels on rails ever conducted. Starting with incomplete work by F.W. Carter from 1930, the team studied conventional two-axle bogies and quickly discovered that, as had been suspected, the problem was dynamic instability. Out of this work came the concept of a critical speed at which point hunting would become a problem. The work was then extended to consider its application to the two-axle wagon designs used on BR, where the problem was further exacerbated by the dynamics of the entire vehicle.
This study resulted in the development of the High Speed Freight Vehicle (HSFV1) design.

During this period, BR's Passenger Business Division produced a report suggesting that rail could compete with road and air, but only if trains were faster. Studying the increase in ridership due to the introduction of the Deltics on the East Coast Main Line, and the effects of electrification on the WCML which improved journey times by 20 to 30%, they concluded that every 1 mile per hour increase in speed would result in a 1% increase in passengers. This basic rule was apparently being proven true in Japan, where the high speed Tokyo-Osaka Shinkansen line had opened in 1964 to huge success

POP train

Although construction of the train was relatively straightforward, a number of more serious problems appeared in the power and control systems. Thus the decision was made to build two additional power cars as unfinished frameworks with no power. These cars would instead be hauled by conventional locomotives to provide data on the tilting and braking systems as well as the dynamics of the vehicles. A contract for the additional two cars was sent out on 14 April 1970, and ran for the first time in September 1971. The name "POP" was assigned, an acronym for "power-zero-power", indicating the two power car layout with no passenger cars in the middle.

The POP train vehicles were skinless and topped with a space frame holding ballast to simulate the various parts of the prospective design. Later a passenger vehicle similar to APT-P design  was added to make a three-car train, at which time the power cars were also plated over the open frames. POP train underwent a number of changes, notably trialling different bogie designs, over its lifetime.


While POP train was proving the basic concepts, construction of the APT-E continued at the RTC Derby. The set was sufficiently complete by late 1971 for an official naming ceremony, where it became the APT-E (for Experimental). It made its first low-speed run from Derby to Duffield on 25 July 1972. Upon reaching Duffield, the ASLEF union immediately "blacked" it, forbidding their members from doing any work involving the train. Their complaint was that the APT-E had a single driver's seat, which they took as evidence that BR was moving to single manned trains. A friendly inspector helped the team move the train back to Derby at night. This resulted in a one-day national strike that cost more than the entire APT-E project.

In August 1973, the 3-car train started a test series lasting eight months, covering the suspension and braking characteristics plus , curving performance and drag. However, reliability was a serious problem and it returned to the shops for a second overhaul in March 1974.
The rebuilt 4-car train returned to service in June 1974. On 10 August 1975 it reached 152.3 mile/h (245.1 km/h) on the Western Region between Swindon and Reading, setting the UK rail speed record. It then set the fastest transit record from Leicester to London St. Pancras when it travelled the 99 miles in 58 minutes 30 seconds on 30 October 1975, at an average speed of just over 101 mile/h (163 km/h) through this sinuous route. It was also tested extensively on the Midland main line out of St. Pancras and at the Old Dalby test track, where in January 1976 it attained a speed of 143.6 mile/h (231.1 km/h).

APT-E testing ended in 1976, and the train was sent directly to the National Railway Museum in York on 11 June 1976, where it was singularly ignored by the NRM for 30 years.


Pendolinos of today have a power car at each end with one pantograph collecting current and power is run down the train with 25kV jumpers between cars to the opposite power car. At the time of the development of an electric version of the APT, the IEE Regulations  forbade the use of 25 kV power jumpers between the passenger cars hence the two power cars were place in the centre of the train. This allowed one pantograph to collect current and to also feed the adjacent power car.

Although the centre power car layout was the simplest in terms of solving the immediate technical problems, it would cause significant problems in operational terms. There was a passage through the power cars that connected the two halves of the train, but it was noisy, cramped and not permitted for passengers. Instead, each end of the train now required its own dining car and similar facilities.

The APT was designed to travel faster than existing trains on the same track. At the APT's design speeds, it would be difficult for the driver to read the trackside signs in time to slow down if needed. Instead, a new system using a transponder-based cab display was introduced called "C-APT". A radio signal from the train energised the track-mounted transponder which then transmitted the local speed restriction. These unpowered transponders were placed at intervals of approx. 1 km. There was a separate cancellation button the cab and like AWS, failure to acknowledge these alerts would result in an automatic brake application.

The hydrokinetic brake system was successful and reliable on the APT-E and was retained for the APT-P with a number of design improvements from the lessons learnt on APT-E.

Service testing

The first power car was delivered from Derby Locomotive Works in June 1977 and the first passenger rake on 7 June 1978, a year late. The first complete train was not ready until May 1979 and it started testing soon after and set the UK speed record at 162.2 mile/h (261.0 km/h) in December 1979, a record that stood for 23 years. Two additional examples were delivered, each with minor changes, one in late 1979, and the last in 1980.

Introduction into service

While the commissioning team continued to report, and solve, problems in the APT design, BR management was under increasing pressure from the press. By the early 1980s the project had been running for over a decade and the trains were still not in service. Press pressure led to political pressure which led to management pressure, and the APT team was told to put the train into operation in spite of its ongoing problems

BR management decided to put the prototypes into service, with the first runs along the London-Glasgow route taking place in December 1981

Following the introduction which was beset by numerous technical failures APT became the focus of a storm of negative press reporting, with every failure extensively reported on and continued claims that the entire project was a white elephant.

Over the next month the air system proved perfectly capable of freezing up even on a full length train. Doors repeatedly stuck, and the braking system could not be trusted. The trains were withdrawn from service at the end of the month.

Back to Main Index

Back to APT introduction