Shortly before the turn of the millennium, Deutsche Bahn and SNCF started a cooperation to develop a modern, single car diesel multiple unit. Partner companies were the French De Dietrich Ferroviaire and German Linke-Hofmann-Busch, both of which now belong to the French Alstom group. Thus, the resulting vehicle was subsequently added to the Alstrom Coradia family, while the “TER” stands for “Transport express régional”, which is used in France for fast regional trains. While in France they are also known by the nicknames „cucumber”, “suppository” and “sausage” because of their shape, in both countries they are usually called “whale” or “blue whale”.

The special thing about the vehicles is that the engines are located at both ends in front of the bogies in the floor and result in a massive appearance. The power is transmitted to the inner axle of the adjacent bogie via a Voith hydrodynamic transmission. This structure allows for a floor height of 55 cm in the middle part, which is positive when used at rural stations without a high platform.

The vehicles were built in both countries of origin, 40 of them in Germany. These are operated by DB Regio as class 641 and are primarily used on non-electrified branch lines. By far the most common variant is the X 73500 of the SNCF, which has a top speed of 140 km/h and of which 312 examples were built. There are also 19 X 73900s for cross-border traffic to the Saarland, which can be used in multiple traction with the German vehicles, and six units from the 2100 series of the Luxembourg CFL.

DB 641 031 in August 2016 in Hof

Simon Scharfenberger

In France, the vehicles repeatedly make negative headlines because they have been involved in accidents at level crossings with barriers failing to close and in incidents when shunting. This was attributed to the fact that the vehicles often do not trigger track circuits for switching barriers or signals because they either have too few axles or, due to their low weight, do not sufficiently displace dirt on the tracks and thus prevent contact closure. As a countermeasure, they are often used in multiple, even if the number of passengers does not require this.

The Type 608 formed a series of six railcars with internal-combustion engines that were delivered by Forges Usines et Fonderies d'Haine-Saint-Pierre shortly before the Second World War. These vehicles were streamlined at both ends, intended for fast traffic without a trailer cars. They were built under license by Ganz in Budapest and offered ten seats in second class and 54 in third class. Both axles of each bogie were driven by an 500 hp eight-cylinder diesel engine via mechanical transmission. 

The six railcars were preceded by a Type 607 prototype that had been delivered in 1936. The Type 608 series vehicles were ordered together with the two-car type 553 railcars and delivered in 1939. They achieved a speed of up to 126 km/h in test drives, but were limited to 85 km/h in service. In contrast to other Belgian railcars, some of them survived the Second World War. It is thanks to this fact that the 608.05 can be visited in the railway museum in Treignes after a refurbishment and is therefore one of only two pre-war Belgian railcars that are still preserved today.

In order to replace the passenger transport capacity on branch lines that was lost during the Second World War, the Belgian state railways procured four-axle diesel railcars of the types 602 and 603 from 1954. A diesel engine from Carels with an output of 400 hp was used as the power plant. The vehicles stood on two bogies, only one of which was driven on the inner axle. This limited their field of application to routes in the lowlands. The differences between the two series were limited to the design of the interior. While the Type 602 also had a first-class compartment and a luggage compartment, the Type 603 only had second-class seats.

The order included six Type 602s and 30 Type 603s. The former served as a feeder to Brussels Airport, while the others served on secondary routes. In addition to the motor cars, trailers were also ordered, which were designated as Type 732 and 734 and had two or four axles.

Types 602 and 603 were later renamed MW 42 and MW 43. After the feeder to Brussels Airport was electrified, the MW 42 were converted into MW 43. As vehicles got older, some vehicles were fitted with General Motors two-stroke diesel engines. This resulted in the MW 44 on the one hand, which was given an engine consisting of two combined four-cylinders and still only driving one axle. In addition, the MW 45 was created, which received two individual six-cylinder engines, each with 165 hp, each driving one axle of each bogie. Other vehicles were converted into railway service vehicles in the 1980s. The last remotorized vehicles were in service until 2002 and were then replaced by the MW 41.

In the years 1934 and 1935, the Reichsbahn procured three subtypes of so-called standard railcars, which were almost identical in appearance and technical equipment and differed primarily in terms of the layout of the interior. The 52 examples that were built made it possible for the first time to convert passenger and express trains almost completely to railcars on a larger route network.

Common features of these vehicles were a length of almost 22 meters, rounded front sides and a diesel-electric propulsion system with engines from Maybach or MAN, mostly with 400 hp. The first six pieces reached 100 km/h, all others 110 km/h. Thanks to lightweight construction with welded car bodies, the weight could be kept at around 50 tonnes. With this power-to-weight ratio, good acceleration could also be achieved with the unpowered driving trailer that was usually carried along. In some cases, trailers were also purchased and the motor cars were also designed for multiple working in order to be able to form trains of different lengths depending on the number of passengers.

The first variant to be built consisted of 20 vehicles, the structure of which was referred to as the “Essen floor plan”. They were created for traffic in West German conurbations and were designed for a quick change of passengers. In addition, they received double sliding doors in the middle and one single door on each side at the outer ends of the passenger compartment. The engine room was located behind one of the driver's cabs. Their running numbers were 137 031 to 035, 137 074 and 137 080 to 093.

This was followed by 20 examples with an express car layout, which did not have the middle doors and were intended for longer distances with fewer stops. They were used in the Ruhr rapid transit and in a large central German network. The latter was concentrated around Halle, Leipzig and Dresden, but also extended as far as Kassel, Braunschweig and what is now Poland and the Czech Republic. The vehicles were designated 137 058 to 067 and 137 075 to 079.

The third design consisted of 17 railcars with a standard floor plan. To ensure a higher passenger flow, they had a large storage space next to the middle double door. Apart from luggage, this was intended for passengers who wanted to get off again after a short time and were thus able to remain standing in this area. The company numbers were 137 094 to 110 and they were also used in the central German network.

After the war, in which some examples were converted into mobile emergency generators, 15 vehicles remained with the Bundesbahn and 24 with the Reichsbahn. Some of the Bundesbahn received new turbocharged engines and three were equipped with a hydrodynamic transmission. Their decommissioning was completed by the mid-sixties. At the Reichsbahn, up to five-part sets were formed. In the case of combinations of two motor cars and three trailers, it was sometimes necessary for a locomotive to push the train uphill. Some examples were redesignated as class 185 in 1970. The last ones were retired in 1978.

The popularity of the two “Glass Trains” ET 91 prompted the Reichsbahn to also order the diesel-powered panorama railcar 137 240 from Fuchs in Heidelberg. It had a similar structure to the ET 91 and was powered by two DWK boxer engines. The engines, along with some other aggregates, were mounted in an auxiliary frame to transmit less noise and vibrations to the passenger compartment. Thanks to the lack of roof equipment compared to the electric multiple unit, the roof was designed to be openable and the frame was reinforced to compensate the lower strength of the roof. The benches were designed with movable backrests so that the passengers could sit in both directions of travel.

Since the design made a good impression, two more examples with the numbers 137 462 and 137 463 were put into service in 1939. One vehicle did not survive the Second World War, the other two were taken over by the Bundesbahn as VT 90 500 and 501. They received new engines and brakes from 1953 and were based in Cologne and Stuttgart. From there they made excursions in a large area until they were retired in 1960 and 1962.

The VT 137 with the running numbers 347 to 396 were diesel railcars for local traffic on secondary and occasionally main routes. Due to their properties, they were also summarized under the designation "225 hp branch line railcars".

The engine was a four-stroke, six-cylinder diesel engine housed in one of the bogies. In contrast to the previous types, these railcars had hydraulic power transmission, which made sense due to the increased engine power. Although the vehicles had regular screw couplers and buffers, trailers were not intended to be attached. This meant that only one powered axle out of two bogies was sufficient, which reduced costs and simplified maintenance. Instead, they had multiple controls. 

For use on secondary lines, the passenger compartment was divided up so that there was only one second-class compartment with six seats and 43 third-class seats. With a maximum speed of 80 km/h, it was also possible to cover parts of the route on main lines. However, this should happen less, since the vehicles originally did not have an Indusi. 

Of the 40 units built in 1939 and 1940, 31 went to the Bundesbahn after the war. There they were called VT 60⁵ and they were adapted to the new requirements right from the start. This included, above all, a more powerful engine with 330 hp. In addition, the layout of the passenger compartment was changed in some and an Indusi was retrofitted. The Reichsbahn only got four pieces and the remaining five ended up in Czechoslovakia. While only one example of the former was still existing in 1970 and it was decommissioned shortly before the planned renumbering to class 185, two of the Czechoslovak vehicles were converted into electric railcars in 1955. The West German vehicles were renumbered as class 660⁵ in 1968, but were retired by 1972.

In Italy in the 1930's there was a need for new vehicles for government sponsored excursions and inter-city express services. The ALn 772 was then developed, with the abbreviation for “Automotrice Leggera a nafta”, standing for “Light Diesel Railcar”. Thanks to modern construction and electrical welding technology, the twin-engine vehicle with 72 seats had an unladen weight of just 37 tonnes.

At each end was a driver's cab with an upright six-cylinder diesel manufactured under license from Saurer. They each had a displacement of 14.3 liters and each produced 150 hp. The engines were spring-mounted in the car body to reduce interior noise and vibration. Since the bogies did not have to accommodate the motors, as was the case with other railcars of the time, cheaper, older designs of bogeys could be used. The power was transmitted via a hydrostatic gear box and allowed a top speed of 130 km/h.

The production should initially take place at the Officine Meccaniche in Milan. Due to initial difficulties with the new production methods and limited capacities, half of the first lot of 200 vehicles was handed over to Fiat. Production was halted during World War II due to other priorities, but later resumed thanks to the Marshall Plan. By 1957, a total of 327 vehicles had been built for Italian customers, including some smaller, private ones in addition to the FS.

Some of the vehicles reached average speeds of over 100 km/h while on duty. They only faced competition from new railcars in the 1960s. In the 1970s, the service increasingly shifted to branch lines. From 1981 onwards, the inspection deadlines gradually expired, so that the vehicles were retired by 1986. Only very few examples have survived today, which is due to the execution of the noise insulation for the passenger compartment. Since large amounts of asbestos fibers were used for this purpose, health hazards arose as the material aged, which made restoration possible only with considerable effort.

After the war, Poland urgently needed new vehicles for passenger transport. Since the ALn 772 had similarities with the pre-war Luxtorpeda, the idea was to procure some of these railcars. Although Poland had too little foreign exchange, it did have high-quality coal. Since Italy hardly had any high-quality coal for the efficient operation of steam locomotives, an agreement was reached on the delivery of three ALn 772 in exchange for coal. Poland analyzed the vehicles delivered in 1951 and made replicas as the SD80. For a longer period of time, they performed their duties in express service and were converted into SR70 railway service vehicles from 1967 onwards.

Since the various existing types of railcars were not suitable for introduction in large numbers, a standard type was developed at the beginning of the 1950s. Experience from the narrow-gauge railcars of the RALn 60 type was applied here. To save costs, they received two commercially available truck engines, each driving one axle. The class 813 of the JŽ and the Y1 of the SJ were derived from the ALn 668.

787 vehicles were built between 1954 and 1981. They were created in several series, which had, among other things, different engines or different door placement. The railcars were usually used individually, but depending on the series they were also capable of multiple working. Specially developed control cars were rarely used because they were only approved for 90 km/h. The ALn 668 were only replaced by the Minuetto at the beginning of the 21st century.