Advanced Passenger Train

In the 1970s, as a response to the growing trend to domestic air travel and private motoring, British Rail attempted to win back passengers with an audacious new high speed express unit, the Advanced Passenger Train or APT, a tilting train that was capable of 160mph, and presented many endearing qualities, being the first train in the world to integrate an active tilting mechanism that would be used to overcome the many winding mainlines of the UK rail network, only for 15 years of trial and error to see the project go from being the bold future of British train travel, to the laughing stock of the industry, falling just short of its goal when the government chose to axe the entire scheme.

The APT owes its existence entirely to the failure of the 1955 Modernisation Plan to address endemic problems with the infrastructure of Britain’s railways, most notably the many bends of primary trunk routes between the nation’s regional centres, with the West Coast Mainline, that runs from London Euston, Birmingham, Manchester, Liverpool and Glasgow, being a prime example, this route meandering along valley floors and around hills for the entire course of its route, but more so when it reaches north of Preston, where the line is forced into the Lune Gorge of Cumbria and over Beattock Summit in southern Scotland, presenting a formidable obstacle for the running of fast trains between London and Glasgow, exacerbated further by the arrival of domestic airliners and the introduction of the motorway network, meaning that faster long and short distance journeys could be undertaken by modes which were perceived to be more convenient when compared to train travel.

Britain’s first moves to accelerate train services began in 1962, when Dr. Sydney Jones of the RAF weapons department at Farnborough was hired by British Rail to investigate a number of infrastructure related derailments in the late 1950’s and early 1960’s, determining that the problem was largely caused by hunting oscillation, a self-oscillation of train wheels between the rails that, if unchecked, led to derailments, this being largely caused by a mixture of high speed operations and poor quality trackwork, with Jones hiring Alan Wickens of Armstrong Whitworth to help determine a solution, and through the use of an incomplete paper penned in 1930 by railway dynamics expert F.W. Carter, Wickens soon discovered that the problem was caused by dynamic instability, and began work in 1964 on the High Speed Freight Vehicle (or HSFV-1), wherein a contemporary freight wagon was tested with a modified wheel design that excluded conventional bogies, and could therefore reach 140mph without suffering from hunting oscillation.

From the information gathered during the HSFV-1 research, the British Rail Board chose to develop the concept further into a high speed passenger train, but the biggest concern of the project was the aforementioned winding nature of Britain’s railways, while limited government subsidies meant that little to no investment existed for large-scale infrastructural alternatives, including the ironing out of tight corners, or the creation of a bespoke high speed line such as the recently opened Tōkaidō Shinkansen of Japan, the world’s first dedicated high speed railway, and one that brought the cities of Tokyo and Shin-Ōsaka to within two hours of each other as opposed to the previous six.

While the use of supereleveation, or canting, was proposed, wherein the running lines were tilted in order to push the centrifugal force down towards the carriage floor, this could only be limited up to 6.5° on a mixed-traffic mainline, as while it would be increasingly effective for high speed services, slow moving passenger trains and freight trains would not be able to travel fast enough to counter the gravitational forces of the tilt, causing passengers and cargo to tip or fall in the direction of gravity.

Therefore, a tilting train was proposed instead, whereby the carriages of the train itself would bend into corners, this concept being pioneered in the United States by the Pacific Railway Equipment Company, when aviation designer William E. Van Dorn of the California Institute of Technology, in conjunction with Northrop Aircraft engineers Eliot F. Stoner and Herbert J. Wieden, developed the first Pendulum Cars in 1937, which utilised a specially designed coil-spring system in the bogies that placed the car body, and the passengers, above the centre of gravity, thus resulting in the car tilting as it entered curves, but while the prototype pendulum cars were used briefly by the Atchison, Topeka and Santa Fe Railway (ATSF), the Chicago, Burlington and Quincy Railroad (CB&Q), and the Great Northern Railway (GN), the pendulum tilt system was sadly not followed up, due largely to the influence of World War II and the expense of the design.

In 1956, the pendulum design was once again revived by SNCF of France, with slight modifications to the previously used American system, but by this stage pendulum tilting systems were being superseded by passive tilt systems developed by RENFE of Spain with the Tren Articulado Ligero Goicoechea Oriol (or Talgo) Pendular, this system being based on a large A-frame, connected to the centre of the bogie, that was as high as the car’s body, at the top of which was a bearing system that swung to either side around the bearing axis, thus causing the carriages to naturally pendulum inward on curves, while dampers smoothed the motion, and following early successful tests of the Talgo method in Spain, the system was trialled in the USA by the New Haven Railroad between 1957 and 1958, and later by the Chesapeake & Ohio Railway (C&O) between 1960 and 1966, culminating in the United Aircraft Corporation TurboTrain gas-turbine powered articulated multiple units of 1968, the world’s first commercial tilting trains.

However, the UAC TurboTrain was not a major success, especially with regard to the tilting mechanism, as the carriage could easily be knocked off balance at low speed, resulting in it swinging and swaying in a distressing manner, while due to the system being passive and relying on bearings and weights, tilting into corners was usually delayed, the result being, after seeing the outcomes of the pendulum and passive systems, BR deciding that an active system controlled by hydraulics would be better, this being developed with the assistance of Dutch engineer A.J. Ispeert, who was hired by Wickens in 1965 to help him create an active tilt system based on hydraulic cylinders that would drive the carriage to the proper angle and hold it there without any unwanted swinging, while also allowing for tilting movement to fit within the limited clearance of the British loading gauge rather than swinging out much further like the passive system.

Combining Ispeert’s research with the high-speed bogie from the HSFV-1 project resulted in the unveiling of the High Speed Passenger Vehicle concept in November 1966, which was presented to the British Railways Board and comprised a dummy car fitted with HSFV-1 bogies and an active tilt system capable of rotating the car at a maximum angle of 9°, which could also be enhanced by through the provision of superelevation to make the most of the train’s cant and reduced influence of centrifugal forces, and once Wickens, with the help of BR engineers Mike Newman and Alastair Gilchrist, had developed a suitable experimental train to test the new active-tilt system, the goal of the project was to deliver a high-speed train capable of 155mph and able to enter corners 40% faster than a conventional train, but the BR Board were less than enthused by the idea, thus forcing Wickens to appeal to the UK government directly.

However, the government was even less enthusiastic than British Rail, and Jones would spend the next two years attempting to appeal the case until finally, in January 1969, a Joint Programme between the Ministry of Transport and the British Railways Board was established, this programme being based on a 50:50 funding basis undertaken over sixteen years with an expiry date of March 1985, creating two projects, the Advanced Passenger Train – or APT – and the Train Control Project, an advanced signalling and train control system that would be introduced to support the APT and higher speed train operations.

Eventually, in May 1969, a prototype APT set, consisting of an articulated four-car unt with two power cars and two intermediate trailers, was approved for construction as a proof-of-concept used for performance monitoring and analysis, while conventional diesel electric engines were supplanted with gas turbine equivalents to reduce the load, with initial considerations being for Rolls-Royce Dart turboprop engines from the Vickers Viscount to be used, before settling instead on Leyland 2S/350 gas turbine powerplants producing 300hp, these turbines being experimental new lorry engines designed by British Leyland, and capable of achieving 156mph, with the space-frame body of the power cars was based on a welded steel tube design derived from Westland helicopter technology, while GEC and English Electric built the intermediate trailers, and British Rail Engineering Limited built the bogies, final assembly of the unit being undertaken at Metro-Cammell’s factory in Washwood Heath, Birmingham.

At the same time, 13.5 miles of the former Melton Mowbray to Nottingham section of the Midland Railway between London and Leeds, which had closed to through traffic in 1968 under the Beeching Axe, was repurposed for use as a test track, and is today known as the Old Dalby Test Track, upon which a rig, which consisted of two converted flatbed wagons with empty space-frames on them, was hauled up and down the line by a Class 17 Clayton diesel locomotive, this set being dubbed P0P or Power-zero-Power, a moniker derived from the fact that the two intermediate trailers were not passenger carriages, with testing of the P0P rig continuing until the end of 1971, after which the new APT set emerged for the first time from the Derby research labs and was christened the name APT-E (or -Experimental).

Six months later, on July 25th, 1972, the set ventured out onto the mainline network, running six miles up the Derwent Valley Line to Duffield on a low speed run, but upon arrival at its destination, the train’s return to Derby was blacked by members of the Associated Society of Locomotive Engineers and Firemen (or ASLEF), the railwayman’s union, which noted that the APT-E had no secondman’s seat, and therefore assumed that the train would bring about single-operation across the BR network and make workers redundant, leading to the train having to sneak back to Derby under cover of night, while ASLEF’s concerns regarding single-operation resulted in a national one-day rail strike that cost substantially more than the whole APT-E project development, the APT-E itself continuing to be blacked by ASLEF for over a year until 1973.

This was somewhat fortuitous, however, as the P0P had illustrated a number of design flaws with the non-driven bogies, which were prone to becoming unstable at high speed, allowing for subsequent modifications to be made to the APT-E, with bogies from the driving motors repurposed for use with the unpowered trailers, the APT-E returning to the mainline in August 1973, and beginning a series of trials on the Old Dalby Test Track, but these ended abruptly after eight months when, in March 1974, the set began to exhibit serious reliability issues that required an overhaul, with the Leyland gas turbine engines being uprated from 300hp to 330hp, while other changes included new motor bearings.

Eventually, the overhauled APT-E set returned to testing in June 1974, and was trailed on the Old Dalby Test Track and the faster sections of the Great Western Mainline between London and Bristol, resulting in the set becoming the fastest train ever to run on Britain’s railways when it attained a maximum speed of 152.3mph between Swindon and Reading on August 10th, 1975, before setting another record on October 30th when it covered the 99-mile journey from Leicester to London St Pancras on the Midland Main Line in a mere 58 minutes and 30 seconds, averaging 101mph and illustrating a massive journey time improvement over the regular loco-hauled services on the route.

Testing of the APT-E continued until May 1976, after which the set was retired immediately to the National Railway Museum in York on June 11th of the same year, having covered an impressive 23,500 miles during its three-year service career, the main reason for withdrawing the gas turbine set being due to the aftermath of the 1973 Oil Crisis, during which the price of fuel skyrocketed, and the thirsty powerplants of the unit were quickly rendered obsolete as drives towards more sustainable power sources were made, resulting in the conversion of the APT project to electric traction when the prototype set, the APT-P, was launched in 1974.

The APT-P, apart from a simple conversion from gas turbine to electric propulsion, illustrated a new series of challenges, primarily due to the positioning and number of pantographs present per train, as it was found that having two pantographs passing across the overhead wires at high speed within close proximity of each other caused resonant waves that damaged the infrastructure, resulting in the stipulation that only one pantograph would be raised at a time, but this led to further concerns regarding the placement of 25kv AC electric equipment within a passenger carriage.

In order to alleviate this, non-passenger power cars would be placed in the centre of the set, essentially splitting the train in half, these powercars providing an overall power output of 2,600hp per car, but caused logistical issues as by splitting the train in two, all facilities in one half-set had to be duplicated for the other half, while the maintenance passageway through the powercars was not suited for public use, further internal problems also being noted due to the train’s sole dependence on the overhead electric wires, as if there was a total power failure, the lighting and air conditioning could not be controlled, rendering conditions inside the carriage unsafe and unbearable very quickly, culminating in the fitting of a small diesel generator to power auxiliary functions in the event of a power failure.

Matters of actually driving the APT, specifically the high-speed operation of the train on existing railways, meant that visual identification of speed signs would also be rendered problematic due to the speed and ability to react in time, thus requiring a new computer-controlled system called C-APT to be developed, whereby a small transponder was placed 1km ahead of an approaching speed restriction that would flag an alert within the cab of the train, with failure to acknowledge the audible alert causing the application of the brakes automatically, while cosmetically, the APT-P differed little from its experimental precursor, retaining the previous articulated bogie design, but with a new system installed that would cause carriages where the tilting mechanism had broken to return to the upright position rather than being left in a helpless tilted position, while the hydraulically actuated friction brakes used for low speed were modified to be fed by a passive hydraulic intensifier rather than a hydraulic power pack.

In total, the APT-P project would consist of eight trainsets of which 80% of the cost would be covered by the UK government, but while the design team attempted to reduce the proposed 155mph top speed in order to simplify the design, British Rail were determined to have a train that could easily outdo both domestic air travel and private motoring, even though concerns were quickly raised that the BR development and research department were investing too much of their time into the APT project, thus causing other proposals to improve the network to be abandoned or put on hold.

In the end, BR were convinced to greenlight another project that would carry over the passenger sector until the full scale introduction of the APT, this being the non-tilting, 125mph High Speed Train (or HST), a diesel-powered express train that would eventually enter service in 1976, but while the HST became a cultural icon that almost single-handedly saved train travel in Britain, its introduction came at the expense of reducing the original eight APT sets to four, and later three following a 1974 government budget review, the result being that, by 1975, the APT project was making very slow progress, and it wouldn’t be until June 1977 that the first APT-P powercar was delivered from BR’s Derby Works, undergoing early testing on the East Coast Mainline behind the former prototype HST power cars, followed a year later by the first passenger vehicles, and, in May 1979, the first full train of two half-sets, designated the Class 370.

Testing of the Class 370 began in the summer of 1979, and in December of the same year it had already broken the speed record for fastest train in Britain at 162.2mph, a record it would continue to maintain until July 2003 when a Class 373 Eurostar set, operating on the partially opened High Speed One would reach 208mph, followed by the arrival of the two other APT sets in December 1979 and spring-1980, each of which had noted minor differences, the arrival of the APT being a highly publicised affair, with a complete set making an appearance at the ‘Rocket 150’ event in May 1980, the 150th anniversary of the original Rainhill Trials that tested the abilities of the first British steam locomotive designs, the APT being propelled past cheering crowds by a Class 56 diesel locomotive, while also introducing to the public the iconic red, white and graphite grey InterCity livery, a stark contrast to the now rather careworn BR corporate blue and grey.

What the public didn’t know was how delayed the brave new face of Britain’s railways actually was, a problem that caused further complications upon the start of testing, specifically issues with the brake units that had been in storage since 1976, these brake cylinders, which had been hastily converted from an oil-based system to a water-glycol-based system, being especially deteriorated due to the anti-corrosion coating having broken down, meaning that even at low speeds the APT sets would struggle to stop within acceptable parameters, while the compressed air systems that operated the brakes and powered doors were also prone to condensation freezing due to the torturous testing regimen of the trainsets, perhaps the most glaring problem with the APT-P was the clearance of the tilting trains themselves, with the potential existing for APT sets, at full inward tilt, to strike one another due to the narrow loading gauge of the BR network, presenting a possibly deadly flaw in the APT’s overall design and operation that could not easily be addressed.

The final major problem the APT faced during early tests was from the BR management itself, when, during a series of cuts in the run up to sectorisation in 1982, the APT development team was disbanded, while BR was still contractually obligated to pursue the APT project until March 1985, thereby ensuring that train testing could continue, but with responsibility for the development of newer train designs being left in the hands of several BR departments, leading, by the end of 1980, to the initial enthusiasm for the train’s unveiling quickly dissipating, and the APT left to face the stringent pressures of the ever-critical national press, with a Private Eye report published in late 1981 highlighting the disastrous development and phenomenal delays the project had incurred thanks to a leak from within the design team, this terrible public relations blow calling BR’s hand, and, despite the ongoing faults with the tilting mechanism and other elements of the train’s technology, the management demanded that the APT-P be put into revenue earning service immediately.

The date was December 7th, 1981, and after being hastily prepared by the maintenance crews at Polmadie Depot south of Glasgow, a Class 370 rolled into Glasgow Central station in order to whisk invited members of the press on a 4 hour and 15-minute journey to London Euston, being able to shave 45 minutes off the journey time, although tragically, in one of the most infamous days in British railway history, the APT’s image was tarnished irreparably when Private Eye released its next issue, placing less emphasis on the train’s improvements in speed and more on the sensation of seasickness felt due to the active tilt system, epitomised by the now iconic “Queasy Rider” headline, to which BR responded by saying the sensation of motion sickness experienced by the press officials was more due to their liberal consumption of the complimentary alcoholic beverages rather than the train, though it was later discovered through various leaks, that the BR design team were fully aware of the motion sickness induced by the tilting mechanism, but due to the APT being rushed into public service they could do little to rectify this fault, the problem being due largely to the delay in the control system to respond to a curve, with the train reacting rapidly after a two to three second lag and therefore giving the impression that the train was about to capsize.

Two days later, during one of the worst winters in British history, the APT-P attempted to make its return run from London to Glasgow, but not long after departure from the capital, the tilt mechanism in one of the coaches failed and was left in a lopsided position, resulting in the set being cancelled at Crewe, leaving the reporters and journalists in the snow, and very soon, the APT had become the harbinger of everything that was wrong with British Rail, with every failure, breakdown or mishap being extensively reported, exacerbated by leaks from within the design team, that noted that only two of the three sets were actually operational, the third being out of service for a prolonged period due to ongoing problems, resulting in the APT being branded the ‘Accident Prone Train’.

Further leaks reported that confidence by the BR management in the train’s reliability was so poor that a relief train, comprised of a conventional locomotive and stock, would shadow the APT around 15 minutes behind in the even there was a failure, while the proposed 155mph top speed was also unobtainable due to the set having to share the mainline with slower freight and passenger trains, forcing it to an operational maximum speed of 125mph, although despite the bombardment of criticism, things weren’t entirely bleak for the project, as following a report published by the consultancy firm Ford & Dain Partners, it was found that, on a technical level, the APT was mechanically sound, with the only issues being due to untrustworthy brake mechanisms and the management structure of the project overall, while solutions as to the motion sickness could be made by slightly reducing the amount of tilt to be deliberately less than needed, which resulted in a small amount of leftover centrifugal force, but this came at the expense of any perceived improvements from the tilting train proposal.

Between 1981 and 1984, development and amendments to the APT project quietly continued, while further variants of the train were established, including the APT-S (or -Squadron) sets, which would comprise of between eight and ten coaches either sandwiched between two power cars or between one powercar and a Driving Van Trailer cab car, as well as an APT set suited for use through the proposed Channel Tunnel, a set that was third-rail compatible for the Southern Region, and a possible diesel-powered APT that could supplement the HST’s, while within the wider project itself, Class 370’s were gradually reintroduced into passenger service throughout the summer of 1984, and were inserted into the schedule on diagrams usually reserved for loco-hauled trains, with passengers unaware they’d be riding one of the new tilting trains until it arrived at the station, responses to the APT this time being a touch more positive, thanks largely to the motion sickness problem having been alleviated, but again, due to the train being unable to tilt to its maximum design capability, these sets were limited to only 125mph, negating their potential speed advantage.

The biggest problem, however, was that the mud had stuck to the APT politically, with the anti-rail government of Prime Minister Margaret Thatcher seeing the train as nothing more than a needless waste of state funding, while also noting the incredible success of the HSTs in delivering fast, modern and efficient train travel to the masses, these factors combined seeing the APT project gradually dismantled in the run-up to the end of its 15-year contractual deadline in March 1985, with the APT-S and other variants being dropped, and the Class 370 sets themselves being withdrawn and placed into storage in the winter of 1985, although it is known that halfsets 370001/002 were still undergoing tests as late as April 1986.

Of these, the first set, comprising half-sets 370001 and 370002, were stored at Polmadie depot in southern Glasgow, but continued to see work operating extra capacity trains in a short-rake formation from Glasgow Central station to Anderston in order to transport journalists and attendees to the Scottish Exhibition and Conference Centre, while 370003 and 006 were initially stored at Crewe Electric depot, but were eventually sold in 1988 by BR to famous DJ, entrepreneur and railway enthusiast Pete Waterman in order to hide it from the condemning eyes of the public at a remote siding adjacent to the Crewe Heritage Centre – which had opened in July 1987, the last set, 370004 and 370005, after being stored at Wolverton near Milton Keynes, ended up at Glasgow Shields Road TMD south of the Clyde, being stripped for spaces before it, and 370001 and 002, were broken up at the C F Booth scrapyard in Rotherham, and Vic Berry Ltd scrapyard in Leicester, respectively.

For the surviving half-sets, 370003 and 006, this complete trainset comprises six coaches, and has been fully restored inside and out so as to provide an internal display to the APT project as well as giving a glimpse as to the passenger accommodation of the trainset, with the tilting mechanism having also been remotely activated on occasion, while one of the two surviving powercars, which wasn’t able to fit within the limited space of the siding, was moved from museum to museum over the course of 30 years before eventually ending up back with the rest of the set in Crewe in October 2017, where it has been cosmetically restored, but doesn’t form part of the preserved trainset.

As for the legacy of the APT, while it has been considered one of the biggest failures in British railway history, the technology behind the concept was sound, and thus in 1986, FIAT Ferroviaria, who had been developing their own tilting train since the mid-1970’s for Italy’s winding railway network, released the ETR 450 in 1988, these trainsets adopting a gyroscopic tilting mechanism rather than the accelerometer-based system used by the British, the Italian system being able to readily detect the change in horizon caused by the start of the parabolic connection that precedes entry into curves, resulting in a smooth tilt into and out of corners that is barely noticeable, the ETR 450 revolutionising express operations on the Italian railway network, and soon gave rise to a family of highly successful tilting trains known as the Pendolino (Italian for Pendulum), this range of multiple units having been developed and improved over the following decades, with new members being introduced even to this day and sold to nations including the Czech Republic, Poland, China, Switzerland, Russia, Finland, Germany and more.

In 2002, tilting train technology came back to Britain in the form of an initial 52 Class 390 Pendolino sets, which were introduced by Virgin Trains to replace loco-hauled stock on the West Coast Mainline between London Euston, Glasgow, Birmingham, Liverpool and Manchester, which, together with a £10bn upgrade to the infrastructure, has seen journey times between London and northern England slashed as speeds were increased to 125mph, while in the case of any other remnants of the APT project, these essentially lived on in the form of the Class 91’s and their InterCity 225 sets used on the East Coast Mainline, the 225s taking the APT-S concept and creating a scaled down version of this technology, building a 140mph capable express train consisting of a locomotive, coaches, and a DVT, while also being designed to incorporate tilting technology if it were ever needed, but this never came to pass.

Overall, it’s hard to comprehend how close the Advanced Passenger Train was to success by the time the project was cancelled in 1986, the operational sets being mechanically sound, but only requiring a few further modifications to the tilting mechanism and the brakes, creating a system that could have not only perfected the tilting train formula for Britain’s railways, but also could have formed the basis of export models that may have been the modern-day equivalent of the Pendolino family.

Instead, poor decisions and management, combined with an anti-rail government, meant that the APT was doomed to failure, and British rail companies would instead be buying back the tilting train technology from foreign builders, while the only remains of the UK’s own endeavours now reside quietly as museum pieces, an example of what should have been a triumph, instead being a calamitous defeat.