These heavy tank locomotives were developed for local service in the Boston area. Due to the tank locomotive design rarely used in the USA, they could run in both directions at high speed. A three-axle rear bogie was used to carry sufficiently large supplies. This led to the 4-6-6T wheel arrangement, which had previously only been used on smaller Mason Bogie locomotives.

In normal operation they often pulled ten steel cars and were apparently able to move up to 20 of these cars with sufficient acceleration. They were regarded as successful all-purpose locomotives, but were only used in the Boston area due to the small number of units. They bore the markings of New York Central for most of their lives. When they were replaced by diesel locomotives in their traditional area of application around 1950, no new purpose was found, so they were probably scrapped in a timely manner.

The Railways Joint Committee for County Donegal procured four tank locomotives to cope with the increasing weight of freight trains. With seven axles and a mass of nearly 45 tons, they were a substantial size for the three-foot gauge. 

According to reports, the boiler originally had a poor steaming performance, which was attributed to an excessive number of heating tubes. Performance improved with the removal of the top row of tubes. In the 1920s, they were all fitted with a superheater, which again significantly increased performance.

The four locomotives were numbered 12 to 15 and named “Eske”, “Owenea”, “Erne” and “Mourne”. Three locomotives were scrapped in 1952 and 1954, but the “Erne” survived until 1968.

In the 1930s, the German steam locomotive industry found itself increasingly under pressure from modern express DMUs. Starting in 1933, Henschel designed the Henschel-Wegmann train, in which both the locomotive and the four passenger cars were streamlined. The class 61 tank locomotive developed for this purpose was only produced twice in different versions, but it proved its efficiency and would probably have been mass-produced without the outbreak of war.

The 61 001, completed in 1935, was a 4-6-4T engine with two cylinders, designed to be as light as possible. For example, the supplies were just large enough to bridge the planned route from Berlin to Dresden. The design as a tank locomotive was chosen so that it could be placed onto the other end of the train at the end of the route without turning, so as not to have too great a disadvantage compared to the express DMUs in this respect. A special feature was the paintwork, which was silver-cream-violet in the same colors as the cars.

Instead of the usual long-tube boiler, a boiler based on Robert Garbe's principle was used, which provided for a long and narrow firebox. When using the usual alloys, this enabled a pressure of 20 bars and also withstood very high evaporation rates for certain time spans without damage. With the 2,300 mm large driving wheels, the locomotive reached up to 185 km/h, so that it was certified for 175 km/h.

Although 61 001 proved to be very efficient, the two-cylinder powerplant resulted in rough running at high speeds. For this reason, road number 61 002 was built in 1939, which had three cylinders. In addition, the rear bogie was extended to three axles in order to be able to increase the slightly too small supplies.

The cars, which were also lightweight and approved for speeds of 160 km/h, could cover the 176 km route Berlin – Dresden in just 108 minutes, which under today's conditions takes more than two hours. The train was able to reach its top speed with the four cars within six minutes. After a break from the beginning of the war, the 001 was only used as a heating locomotive, but the 002 was used again for express service from the end of 1940.

After the war, road number 61 001 came to the Bundesbahn, where the one-off was stationed in Bebra and, after the cladding was removed, was used until an accident in 1951. After that it was not refurbished and scrapped in 1957.

Road number 61 002 stayed with the Reichsbahn in Dresden and was increasingly used there for test runs at high speeds, since the repairs were too expensive for regular traffic. In 1961 it was converted to a tank locomotive, road number 18 201, which received a new boiler and parts of the test engine H 45 024. It reached speeds of up to 182.5 km/h and is still in regular use today.

A tank locomotive for passenger trains had already been developed with the Prussian T 18, which could reach speeds of 100 km/h in both directions. In order to have a powerful engine of this type also for main routes with terminal stations, the class 62 was developed as part of the standard program. It was also given the symmetrical wheel arrangement 4-6-4, but was heavier with an axle load of 20 tonnes and achieved a significantly higher output than the T 18.

In 1928, 15 of these locomotives were built in typical standard design. They had a two-cylinder superheated engine that achieved an indicated output of 1,680 hp. In order to improve driving characteristics over longer distances, it was fitted with coupled wheels that had a diameter of 1,750 mm and were therefore 10 cm larger than those of its prototype.

Since the Reichsbahn apparently had too few routes in 1928 on which the class 62 could play to its strengths and their unit price was felt to be too high, only two examples were taken over that year. Finally, in 1932, the remaining 13 were taken over. Areas of application were, for example, the Werrabahn or metropolitan areas with shorter sections and terminal stations.

After the end of the war, all locomotives were still in service. Seven of them now came to the west and eight to the east. As is usual with the Bundesbahn for rare types, the class 62 was not to be kept in stock for long and was therefore phased out by 1956.

With the Reichsbahn, most of the engines were located in the north. Some of them were later given multiple controls so that they could be used with the modern double-deck coaches. In 1970 there were still three of them, these were also retired by 1972.

In order to be able to haul heavy passenger trains with a maximum axle load of 14 tonnes on branch lines, a tank locomotive with seven axles was required. Thus, the Reichseisenbahnen ordered a total of 66 locomotives from Grafenstaden in several batches with the 4-6-4T wheel arrangement and de Glehn four-cylinder compound engine. Although the locomotives briefly delivered almost 1,000 hp, they quickly reached their limits due to the low adhesive weight. After the Second World War, most of these locomotives were in Germany. Most of these came back to the SNCF and were retired by 1954. The Luxembourg CFL had also received some in the meantime.

In 1917, two tank locomotives were built in the Addington workshops with boilers that were originally intended for class A^B Pacifics. These now had an additional trailing axle and many common parts with the Pacific, which simplified maintenance. Two almost identical variants were built in series, which were designated as W^AB for use on main lines and as W^S for use in suburban traffic. Between 1947 and 1957, some W^AB were replaced by other locomotives, after which eleven were rebuilt into class A^B tender locomotives. In the sixties the remaining W^AB were retired.

In order to improve the operation of steam locomotives on winding mountain routes, the T 16 with the number “Erfurt 1980” was developed for trial use on the mountain routes in the Thuringian Forest. Its distinctive feature was a second cab at the front to improve visibility of the track. It was not mass-produced and should therefore not be confused with the later freight locomotive T 16 with 0-10-0T axle arrangement.

A symmetrical chassis with the wheel arrangement 4-6-4T and 1,750 mm large driving wheels was used as a basis to enable a speed of 90 km/h in both directions. The requirements stipulated that these locomotives should be able to pull 200-tonne trains at top speed on level ground and up one percent steep gradients at 75 km/h or 47 mph. As with the two S 9 trial locomotives that were built at the same time, a third man was deployed in the front cab because the fireman was unable to operate the engine on his own. There was a voice connection between the cabs in order to be able to give the appropriate instructions based on the observations on the route. In contrast to the S 9, the front was not tapered due to the lower speeds.

With its extremely generously dimensioned grate area and the equally large evaporative heating surface, the locomotive was able to achieve a high level of continuous output. However, the complex operation with the two cabs was not convincing and therefore there was only one example, which was only used sporadically. A real successor was the T 18 from 1912 with the same wheel arrangement, which was conventionally equipped with only one cab and was still able to provide sufficient performance with a simple engine.

When the engines of the classes T 10 and T 12 had reached their power limits, the T 18 was developed as the last tank locomotive for passenger trains, which was still taken over by the Prussian State Railways. Due to their successful construction, further orders could also be received from other railways at home and abroad. In order to be able to avoid turning the locomotives at the ends of the route and to be able to drive the same speed in both directions, a tank locomotive with a symmetrical wheel arrangement was chosen. Tender locomotives, which could also reach high speeds in reverse, only appeared later, and in the case of tender locomotives with an asymmetrical wheel arrangement, the running smoothness when reversing was usually not entirely convincing.

The resulting T 18 had a leading bogie, three coupled axles with a wheel diameter of 1,650 mm and a trailing bogie and, with full supplies, had an operating weight of 105 tons. In order to be able to negotiate tighter curves despite the long wheelbase, the bogies were each designed to be laterally displaceable by 80 mm and the wheel flange of the middle coupled axle was weakened by 15 mm. The inside of the plate frame was used as a third water tank in addition to the two water tanks on the sides of the boiler. This resulted in relatively large reserves of water and coal for a tender locomotive. The first nine pieces could reach a maximum of 90 km/h, all others 100 km/h. With an indicated output of 1,140 hp, trains of 350 tonnes were pulled at 90 km/h on the flat, and 315 tonnes at 60 km/h on a gradient of 0.6 percent.

The first engines were delivered in 1912 by Vulcan in Stettin, others by Henschel and Hanomag. A total of 534 engines were built, most of which went to the Prussian State Railways and later to the Reichsbahn. In addition, Württemberg received 20, Alsace-Lorraine 27 and the Saar region also 27 pieces. Two more were later given to the Eutin-Lübeck railway. The Turkish State Railways was a foreign customer for the T 18.

From 1925 the locomotives became the class 78 and their number only decreased slightly until after the Second World War. In the end, the Bundesbahn took over 424 units and the Reichsbahn 53. Some of the former were equipped for push-pull operation, with the regulator being remote-controlled via an electric motor and compressed air. The locomotives remained in use on both railways until the 1970s. Today there are still six vehicles, some of which are operational, but some of which are not open to the public.