APT vs HST - P V Amor

Perfect is the Enemy of Good Enough: APT vs HST


In the 1960s, British Rail had a problem. Passenger numbers were down hugely, and money was being lost hand over fist. The Beeching reports and numerous other cutbacks had left the network far smaller than it had been when they inherited the network in 1948. This had left British Rail, despite a comprehensive rebranding programme, with a poor public image.

Furthermore, the railways no longer had a monopoly on long distance transport. Cars were now more reliable and affordable than ever, and new motorways and dual carriageways were being built across the country. The future, it seemed, lay with motoring. Furthermore, aircraft were fast, glamourous and luxurious, and airports were growing across Britain, presenting a faster alternative to rail on many routes.

Although British Rail was rapidly getting rid of steam locomotives, journey times were still relatively high with the new diesel and electric traction. Rolling stock was still fairly old fashioned; air conditioning was the exception rather than the rule, and modern interior design was almost unheard of, at least until the newer mark 2 coaches. It was decided that something must be done to compete directly with the airlines and motorways.

Radical engineers were brought in, some from the aviation industry, and they immediately discovered a problem. You see, Britain’s railways are full of curves, mainly because they were built by Victorian engineers, keen to avoid clashes with irate landowners and expensive civil engineering. Now you could build new, straighter railways, as many countries, notably Japan and France, did (we’re now doing this with HS2), but British Rail was in no position to do this, being cash strapped after all.

Trains can travel around curves relatively quickly, but this makes passengers inside very uncomfortable, as they are thrown to the outside of the curve. The engineers noticed that motorcycle riders also have this problem – so they lean into the curve. This cancels out the centrifugal force on the motorcycle and rider, allowing the motorcycle to corner quickly. So they decided to apply this to railways, and tilt the body of the train into the curve.

The tilting train idea was given the term “Advanced Passenger Train” or APT, and by 1972, a working prototype, the Advanced Passenger Train – Experimental or APT-E, had been built. This was, by and large, a success, and although it only consisted of 2 power cars and 2 coaches, it was still very fast, and the tilt worked as intended.

Unfortunately, the APT-E was powered by gas turbines, an innovative propulsion system but unfortunately a very thirsty one. This wasn’t an issue in the 1960s, as oil was plentiful and relatively cheap. However, with the oil crises of the 1970s, this was no longer the case. The APT-E, following relatively few tests, was withdrawn. Preparations began to be made to produce a production version, powered by electricity. It was dubbed the “Advanced Passenger Train Prototype” or APT-P.

It was 1978 when this finally appeared, and it was a rather different animal. The train was now propelled by 2 electric power cars in the middle of the train (packing 4,000 hp each), with coaches on either side (more on this later) which featured proper passenger accommodation and catering. Access was via compressed air powered doors, and the construction was similar to an aircraft’s, an aluminium monocoque, which made it much lighter than British Rail’s usual trains, and far more energy efficient. It also looked radically different to anything on British Rail at the time.

Not only was the new train capable of tilting, it was also very fast in a straight line. The APT-P was worked up to speeds in excess of 160 mph on test, on conventional track, though due to signalling constraints, it would travel at 125 mph in standard service, still faster than all conventional trains on the West Coast Mainline. Many within British Rail felt they were onto a winner, and, on the surface, it seemed they had a point.

However, some in British Rail had other ideas. You see, BR’s traditional engineers didn’t like all this radical interference in what had been their matters. They reckoned they could deliver a 125 mph, air conditioned diesel train, using conventional technology, operating on conventional track, by 1975. This train wouldn’t tilt, but on a relatively straight main line like the Great Western or East Coast, it would be far quicker than the then current rolling stock, and importantly, it would be at a fraction of the cost of the APT. British Rail decided that this project would also go ahead, as a stop-gap before the APT could be brought in. It was given the name High Speed Diesel Train, HSDT.

Again, by 1972, a prototype was ready, with a diesel power car at each end, and it was tested up to a speed of 143 mph. Passengers on press runs were impressed by the smooth ride of the new mark 3 coaches that formed part of the train, as well as the internal sliding doors, operated by a treadle under the carpet. Following these tests, preparations were made to engineer a production version, to go into service on the relatively straight main line between London and Bristol.

Determined to make this a success, they brought in the industrial designer Kenneth Grange, who turned the rather ugly HSDT into the beautiful, iconic Inter-City 125, or just High Speed Train, or HST. Following a period of trains being interleaved with regular services, the train entered full service, at 125 mph, on October 4th 1976, admittedly a year later than promised. It was a phenomenal success, popular with passengers and crew alike. Inter-City 125 became a household name, and British Rail milked the publicity for all that it was worth, producing numerous badges, posters and television advertisements featuring their new train.

Meanwhile, things began to go wrong with the APT-P. While initial trials had gone well, there were troubles with reliability and costs were soaring, much to the chagrin of the new Thatcher government. Thus, the decision was taken to put the APT-P into service on a limited basis, to show that British Rail was giving the public something for their money. The service began in early 1980.

To put it mildly, this was not a success. The compressed air powered doors suffered from problems as water got into the system and froze in the winter, so the doors were unreliable. As the power cars were in the middle, people couldn’t get between the coaches, so to avoid people all jumping on the rear of the train at the last minute, they had to book a seat in advance. This was the least of their problems though, as the power cars had not been properly weatherproofed. The winter weather played havoc with the train, with consequent bad publicity.

Worse still, even when the train worked, it was making people sick. The tilt which was supposed to remove discomfort actually did cause some discomfort, because when the train rounds a curve, you expect to feel a centrifugal force. If you were looking out of the windows, this would result in a sensation not unlike sea sickness. BR also decided to serve alcoholic drinks to members of the press on the train, which made the problem feel even worse.

What could have been a revolutionary breakthrough in train technology became a national laughing stock. APT was routinely mocked on television, in the newspapers and on the radio, with British Rail made to look thoroughly incompetent at every turn (or tilt). Much of the criticism was unfair, but sadly with the press, this did not matter.

British Rail management lost their nerve and withdrew the APT-P trains. The project was officially cancelled, though work would continue for the next few years as a technology demonstrator. If you were lucky, one of the APT-Ps might turn up on a relief train, but British Rail did not publish the times they would be deployed, almost as if they were ashamed of the train. However, many of its reliability problems were solved, and its tilt reduced slightly to eliminate the sickness problem. The plan to eventually produce a huge fleet of APTs was scrapped, though much of the technology would be incorporated into the InterCity 225 electric trains for the East Coast Mainline.

So where are we now? One of the APT-Ps was hushed up in Crewe, where it can still be seen at the Heritage Centre. The tilt is still operable, and is occasionally powered up for demonstrations. This potentially revolutionary piece of technology now rots away, almost bereft of publicity. Having spoken to people at Crewe, it is clear that it would take many, many millions to bring the APT-P back to mainline operational standard, and it is unclear who would undertake such a venture.

The APT-E now forms part of the National Collection, and can be seen at the National Railway Museum Shildon. Occasionally, tours are given of the train, and it has been cosmetically restored, though it is unlikely to run again. On test, it had only covered a measly few thousand miles, but its gas turbines are extremely non-standard in railway terms.

Oddly enough though, that isn’t quite the end of the story. The patents generated from the APT were sold abroad. Years later, the Pendolino, another tilting train, was introduced to the UK by Virgin, incorporating much of the technology developed for the APT. In essence, the technology has been sold back to us, although in a train that has nowhere near the number of problems of the APT. Importantly, the Pendolino has its electronics beneath the floor of the train, so you can walk through the entire thing, no awkward booking required, and with Virgin’s publicity machine, the Pendolino has been a phenomenal success.

What of the HST? Well, HSTs still form the backbone of UK intercity trains today, over 40 years later, with some relatively minor refurbishment. The original Paxman Valenta engines, while powerful and light for their day, were also extremely loud and had relatively short lives. In the mid 2000s, these engines were replaced with either modern MTU engines from Germany or home-grown Paxman VP185 engines. Head and tail lights were also replaced, but few other modifications needed to be made.

The mark 3 coaches were used not just for the HST, but also for many electric locomotive hauled trains, some of which are still in service on the Great Eastern Mainline between London and Norwich. The mark 3 continues to receive praise for its ride quality, crashworthiness and comfortable seating, and with modern upgrades such as plug sockets and Wi-Fi, they remain a favourite with passengers.

Only now are the HST’s replacements (the Intercity Express Programme, or IEP trains) fully being introduced, and even then, it is taking far longer than it was supposed to. The IEPs have also had teething troubles – on the first service run, an air conditioning unit malfunctioned and literally poured cold water on passengers (though this hasn’t happened since). There have also been many complaints about the new interiors, as compared with the older HST ones. Eventually, these issues will be solved, but it just goes to show how good a design the HST is.

Even then, after a thorough refurbishment, including power-operated doors and a shortening to 4 or 5 coaches to improve acceleration, some HSTs are being deployed in Scotland as fast, intercity trains, without the need for great expense. Sound familiar?

© Peter Vincent Amor 2018.

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Last Revised: 26.03.2021 9:42
by R G Latham
© 1998