Since it became apparent in the seventies that electrification of all main lines would not be possible, British Railways had a diesel-powered high-speed train built. In order to keep the axle loads low, a streamlined locomotive with a fast-running and light Paxman Valenta with 2,250 hp is used at each end of the train. The trains reach a service speed of 125 mph or 201 km/h and were initially classified as class 253 and 254 multiple units. Only later were they renumbered into class 43 locomotives.

The trains run with a variable number of Mark 3 coaches and quickly spread across Britain. They are officially simply called “HST” (“High Speed Train”), but were also used as “Intercity 125” in reference to their top speed. They significantly shortened travel times compared to trains with conventional diesel locomotives. With a record of 148.5 mph (239 km/h), they are considered the fastest diesel locomotive in the world.

National Express HST with 43309 at the top in January 2009

Phil Sangwell

With the privatization of British Railways, the HST came to a variety of operators. The new VP185 engine was developed before privatization, but was only installed in some of the vehicles. After the turn of the millennium, more were re-engined with new MTU engines. At the same time, some of them were replaced by new multiple units, such as the families of the 220 and 800 classes. However, due to the increased number of passengers, many remained in service. Even after 2020, many HSTs were still active in passenger transport. Today some are used by Network Rail or to ferry trains. Some were even exported to Mexico and Nigeria.

The VT 11⁵ was developed in the 1950s as a trainset for the high-quality connections of the Trans Europe Express. It was the flagship of the German Federal Railways until it gradually became less important due to progressive electrification and the introduction of new train types. The trains consisted of one power car at each end, between which five trailers were usually running. These consisted of two compartment cars, an open seating car, a dining car with a bar and a kitchen car with an additional dining room. The TEE only carried first class, like the Intercity that was introduced later.

The power cars used the same drive train technology as in the locomotives of the V 100 and V 200 classes. These were diesel engines from MTU or Maybach with 760 or 810 kW and hydraulic power transmission. Only the two axles of the front bogies were powered.

A special type was the class 602, from which four power cars were created in 1972 from converted 601s. Gas turbines with 1,617 kW each were used for power. A train with two trailers set a record of 217 km/h, but usually up to ten cars formed a trail running at 160 km/h.

From 1957 the trains were used as TEE and switched to the IC in 1971 when this type of train was created. Since the technical equipment allowed more than the previous 140 km/h, the certified top speed was changed to 160 km/h at this time. In 1979, the Bundesbahn also introduced the second class of coaches for the IC, which meant that the multiple units with their special design and low passenger capacity were no longer suitable for these trains. They were therefore used in tourist traffic with ten cars, with significantly poorer performance than with five cars. In 1987 and 1988 all remaining units were sold to Italy. A ten-car train, which the Reichsbahn had borrowed from Italy in 1990 and used between Berlin and Hamburg for a few months, had a last short scheduled use in Germany.

The train set with the number 137 155, also known as the Kruckenberg express railcar, was the prototype for a future-oriented design of light and fast diesel railcars. Although only one example was made, almost exactly the same design was used on both sides of the Iron Curtain to develop their own multiple units after the war. These were VT 11⁵ for the Bundesbahn and VT 18¹⁶ for the Reichsbahn.

The train was made up of three parts and had a motor car at each end, which also accommodated some passengers. Each motor car had a turbocharged Maybach diesel engine with 600 hp, which delivered its power to one of the two axles of the front bogie via a hydraulic transmission. At the gangways between the cars, the adjacent cars shared a Jakobs bogie. Other features of the vehicles were the lightweight construction and air suspension.

Although the drive shafts broke during testing, a new speed record of 215 km/h was set on June 23, 1939. Since the entire express service had been discontinued shortly before the outbreak of war, no further sets were ordered. After the war, the SVT 137 155 was no longer used. It was located in the eastern zone and after a few years in the scrapyard it was officially retired in 1958 and only scrapped nine years later. The two multiple units developed later in the west and east had almost the same design and also had raised driver's cabs behind the engines. With these, however, each car had two independent bogies instead of one Jakobs bogie between two cars.

After normally only supplying passenger coaches in the past, Talgo introduced a complete diesel multiple unit in 1999. This consisted of one or two powered end cars and Talgo 7 trailers, which had the typical passive tilting technology. Trains with a powered end car were to run with 1,800 kW, four trailers and a control car. Engines with only 1,500 kW each were planned for two power cars, as well as up to twelve trailers. The gauge of the bogies can be changed on stationary gauge-changing devices while running through slowly.

What is special about the drive technology is that the hydrodynamic transmissions are located in the car body and the brake discs are also located on the cardan shafts. The vehicles are designed for 220 km/h and an unofficial record is 256 km/h. As a set with only one powered end car, a maximum speed of 160 km/h was only permitted when driving with the control car ahead.

Only two power cars were built in total. A possible area of application would have been in Sardinia, where a train demonstrated a significant reduction in travel time. Ultimately, there was no series production, as vehicles from CAF were ordered instead. After testing, the built vehicles went to the Spanish infrastructure operator Adif. One train is used here for overhead line measurement runs. This consists of a power car, two trailers and a control car, which has been given a pantograph for this purpose.

The United Aircraft Corporation developed the TurboTrain to accelerate the only partially electrified section of the Northeast Corridor between New York City and Boston. Each power car had slots for a maximum of seven turbines, each with 400 hp, five of which were actually used. In the tunnels in New York City, electricity could also be collected via the third rail. As with Talgo, the cars were hung on single-axle Jakobs bogies with passive tilting technology. The train was certified for 120 mph and reached 100 mph in service. A speed of 170.8 mph was reached on a test run. Two trains were ordered by New Haven and later came to Amtrak. Five more went to Canadian National and later came to VIA Rail. Although they significantly reduced travel times, they had many teething problems that could only be partially remedied. Amtrak only used the trains until 1976 and VIA until 1982.

After the M-10000 to M-10002 had been built as different individual trainsets, the M-10004 to M-10006 and the M-10003, which was delivered later, were the first to be built as several identical streamlined multiple units. The M-10004 was intended for the “City of San Francisco” between Chicago and San Francisco, while the M-10005 and M-10006 were used for the “City of Denver” between Chicago and Denver.

Each set initially consisted of a power car with a driver's cab, another booster, nine passenger cars and a lounge car with a rounded rear. The front design deviated from the tower-like driver's cab of the predecessors and followed the carbody design, which later diesel locomotives also picked up. The nose was dominated by a very large grille and a snow plow, which showed a lot of chrome. The unit of power car and booster, numbered M-10003, was eventually built as a reserve to replace failed units.

In each power car and booster was a 1,200 hp Winton 201, which was later also used in EMC's E-series passenger locomotives. The generator, the electrics and the four traction motors each came from General Electric. The associated passenger cars were each designed with a low profile to match the powered cars. A total of six of the cars were connected in pairs to Jakobs bogies. 

M-10004 was exchanged for a locomotive-hauled train in 1939. The power cars and the already decommissioned M-10001 were used to reinforce the other three trains by a third unit each. This increased the power per train from 2,400 to 3,600 hp, which also allowed additional cars to be attached. They were used in this combination until 1953 and then replaced with conventional trains with E-series locomotives.