The DL-103 to DL-110 were the first diesel locomotives built by ALCO. The DL only stood for “Diesel Locomotive” and the individual models hardly differed from each other. The odd numbers stood for normal locomotives with cabs (so-called A-units), while the even numbers denoted the cab-less B-units or boosters. As with most American diesel locomotives of the time, the carbody was designed as a self-supporting construction with a streamlined front. The shape of the front with the three-piece windshield was designed by the German-American industrial designer Otto Kohler. All locomotives had an output of 2,000 hp, which came from two six-cylinder inline prime movers with turbochargers. Although four traction motors were sufficient to transmit the power, three-axle bogies, each with a carrying axle in the middle, were used, as in the EMD E series.

A total of 74 A units and four B units were built between 1939 and 1945. By far the largest proportion of these were the 60 A units ordered by the New York, New Haven & Hartford Railroad. All other customers received a maximum of four units, which were often used in front of prestigious passenger trains. The Second World War had made procurement difficult, since the production of purely passenger locomotives was prohibited and locomotives that were equally suitable for freight and passenger trains were also difficult to obtain. Finally, the New Haven only used their locomotives to haul passenger trains during the day, while hauling freight trains at night. Between 1949 and 1951 they were modernized and, among other things, the side windows in the engine room were removed, which were only used for decorative purposes. Despite this, the locomotives' service life was not very long, as they were soon replaced by more modern locomotives. Some were still visually matched to their EMD competitors, but most fell victim to the scrap press in the 1950s.

With the development of the new Type 244 engine, ALCO introduced the PA passenger locomotive in addition to the FA freight locomotive in 1946. Not only did the propulsion electrics come from General Electric, the streamlined and modern design of the car body also came from Ray Patten, head of GE's design department. The PA got the more powerful sixteen-cylinder engine and stood on two trucks with the A1A wheel arrangement. What all PA and FA have in common is that black smoke came out when accelerating due to the lack of air in the turbo lag.

With a 2,000 hp engine, 169 PA1 and 39 PB1 without a cab were built. From 1950 onwards, 81 PA2 and eight PB2 were built with 2,250 hp. Three PA-2s went to Brazil with a gauge of 5 ft 3 in. Some railroads also used their PA and PB in freight traffic, but the number of units remained behind EMD's E series due to lower reliability. The Massachusetts Bay Transit Authority used its locomotives until the late 1970s and then sold them to the Ferrocarriles Nacionales de México, which continued to use them until 1981.

Baldwin's first attempt at a diesel road locomotive was the DR-12-8-1500/2, which was also called the “Centipede” because of its many axles. Each locomotive had one cab and two bogies, which in turn were divided into four powered axles and a two-axle leading bogie. Power was provided by two eight-cylinder engines with 1,500 hp each.

The type designation was formed from this data, as well as the total number of twelve axles with eight powered ones. Usually two locomotives with a total output of 6,000 hp were coupled together. The UP initially ordered two Centipedes, which were not accepted and were then used together by Baldwin as demonstrator.

The series variant was ordered by only three railroads. The largest customer was the Pennsylvania Railroad with 24 Centipedes, which were later provided with a shorter gear ratio for freight traffic and were derated to 2,500 hp. Seaboard Air Line and Nacionales de Mexico each ordered 14. The NdeM locomotives were later equipped with multiple controls and used as helper locomotives. Ultimately, all Centipedes were scrapped because they could not assert themselves against their competitors.

The ten prototypes with the numbers D200 to D209 were delivered in 1958 as the first large diesel locomotives to be series-built by English Electric. They were based on the three experimental D16/2 completed in 1950 and 1954. Like the third D16/2, the production variant still used the same 16SVT engine with 2,000 hp and the same bogies. The bogies, each with three powered axles, also had a leading axle each in order to be able to carry the heavy weight. The body of the production locomotives deviated from the D16/2 and already had the shapes that were later to be found on the classes 37 and 55.

Another 190 production locomotives followed until 1962 as the D210 to D399, which later became known as the class 40. The first batch only received a vacuum brake system, the later ones could also haul cars with air brakes. Since they were intended for use in front of passenger trains, all received steam heating. Even during their testing, some people considered the power for a large locomotive with such a high weight as too low. During the production of the last batch, the locomotives of classes 47 and 55 were introduced, which developed a significantly higher power at a lower weight without unpowered axles.

The class 40 was primarily used in the north of England in front of high-value passenger trains. On the large main lines they were soon replaced by more powerful diesel locomotives, but on other lines they initially had no major competition due to their low axle loads. The lack of electric train heating became their problem from around 1980, as fewer and fewer passenger cars with steam heating were available. In contrast to the class 37, the class 40 was never rebuilt, so that more and more withdrawals began and in 1985 the last disappeared from the scene. A total of eight locomotives were preserved, some of which are still operational today.

In the fifties, British Railways searched for a way to replace the fastest steam-hauled express services on the East Coast Main Line between King's Cross and Edinburgh. Since electrification of the complete ECML was not foreseeable in the near future, this had to be a diesel locomotive that could reach a higher average speed than the streamlined A4 Pacific. The answer was the DP1 prototype completed by English Electric in 1955. It was the most powerful single-unit diesel locomotive in the world at the time of its introduction into service.

The solution for getting as much power as possible from a six-axle locomotive that was not too heavy for high-speed running was the Napier Deltic engine. This was a two-stroke opposed-piston diesel engine inspired by the German Junkers engines of the thirties. In this case, it was combined of three banks of six cylinders each which were mounted in a triangular layout with a total of three crankshafts. Although not turbocharged in its original form, it could deliver 1,650 hp with its high running speed of 1,500 PRM at a low weight compared to other diesels of the time. Each locomotive had two of these engines with one generator each.

In 1961 and 1962, 22 production locomotives were completed. Officially called “English Electric Type 5”, they were usually called “Deltics” and later became BR class 55. Apart from their power, they became famous for their appearance with their great length and their bulldog noses inspired from American diesel locomotives. Although officially limited to a top speed of 100 mph or 161 km/h, they could complete the journey of the “Flying Scotsman” in six and a half hours, half an hour faster than the A4, due to their faster acceleration.

In the years after the introduction of the Deltic, the ECML was upgraded for higher running speeds. In daily service, they sometimes even exceeded 100 mph, further decreasing the running times. The highest speeds recorded were 117 mph (188 km/h) on the level and 125 mph (201 km/h) on downward stretches.

A downside of the Deltic engine was its complexity and complicated maintenance, so that more engines had to be held in spare to ensure the availability of the locomotives. With the introduction of the class 43 High Speed Train on the ECML, the Deltics became superfluous. After only a short time in secondary services, they were all withdrawn in 1980 and 1981 after less than 20 years in service. Six have been preserved, all of which have run in preservation.

For use as a future type 5 locomotive, Brush Traction built a single technology demonstrator in 1967. It was designated HS4000 after Hawker Siddeley, the owner of Brush and the horsepower rating of its engine. The engine was an oil-cooled V16 from Sulzer, with the idea that a single engine would be easier to maintain than two. To enable a top speed of 110 mph (177 km/h), it had hollow shaft drive and dynamic brakes. 

After being handed over to British Railways, it was tested in freight and passenger service. No additional orders followed since its axle load was too high for many British lines. In 1971, it was sold to the Soviet Union where it was put on display, re-gauged to Russian gauge and tested. After some years of service, it was finally scrapped.

In 2009, the Argentine state railway Trenes Argentinos ordered 20 CKD8 diesel-electric locomotives from the Chinese company CNR, together with 220 passenger coaches for long-distance traffic. Although they have six axles, they are only intended for use in front of passenger trains.

The engine used is the MTU 16V 4000 delivered from Germany, which has an output of 2,200 kW. 13 CKD8G and seven CKD7G were built for different lines. The CKD8G reaches 120 km/h, while the CKD8H is designed for 160 km/h and therefore has a lower tractive effort.

Another order came from Nigeria in 2014 and included the CKD8 for the upgraded route between Abuja and Kaduna. These locomotives have been in service since 2018 and have a top speed of 150 km/h.

To speed up heavy passenger trains, China Railways started development of a heavy diesel-electric locomotive in 1990. After two DF9 prototypes built for a service speed of 140 km/h, the first DF11 built for 160 km/h was completed in 1992. At a weight of 138 tonnes, it is powered by a sixteen-cylinder with a rated power of 3,860 kW (5,176 hp), calibrated for 3,630 kW in the locomotive. Six DC traction motors have 3,040 kW (4,077 hp) in total.

On test runs, these locomotives could reach a speed of 184 km/h. A normal train load when running at top speed is 640 tonnes, but even passenger trains of 1,100 tonnes can be hauled at a speed of 143 km/h. As with previous Chinese locomotives, they can't deliver head-end power to the train, so separate generator cars are needed.

There is also a special plateau type for service on the highland plains in Western China. These have special filters for running through sandstorms, a slower gear ratio for a top speed of 153 km/h and engine modifications for greater power at altitude. Up to 2005, a total of 459 DF11 have been built for service in several regions of the country. Today they are still omnipresent on many non-electrified lines.