The Three-Power Boxcab was developed in the late twenties for operation on both electrified and non-electrified lines in regions which prohibited the use of steam locomotives. When they worked on electrified sections, they could pick up lineside direct current, while primarily using battery power on non-electrified sections. The batteries were charged by a small diesel engine that could be switched off when running through stretches which even did not allow diesel fumes.

These locomotives were built by ALCO with electric components from General Electric, engines from Ingersoll Rand and batteries from Electric Storage Battery. The prototype from 1928 had a central cab, while the production locomotives had two end cabs. While the maximum output in electric mode was 1,580 hp, the 300-hp engine could only slowly recharge the batteries with a 200-kW generator. The batteries had a total capacity of 301 kWh, what meant that a complete recharge required one and a half hours with the diesel running at full power.

The locomotives were also called “oil battery electrics”, since the name “Diesel” was unpopular in the USA in this period. From 41 locomotives built, most went to the New York Central as class DEs-3. One went to the Rock Island and others to Chicago, Detroit and Boston. Most were equipped with contact shoes for 600 V DC, but two instead with pantographs for 3,000 V DC. Most were retired in the sixties and seventies.

Several non-electrified commuter lines are located between New York City and several cities in New Jersey. However, since the crossing under the Hudson River can only be used by electric locomotives, passengers used to have to switch from diesel-powered trains to other trains. In order to ensure an uninterrupted journey, New Jersey Transit originally ordered 26 passenger locomotives with fully-fledged diesel and electric power trains from Bombardier in Kassel in 2008, with options for a further 63. Because Canadian operator Exo, then AMT, which operates commuter rail services around Montreal, had the same problem with the Mount Royal Tunnel, they joined NJ Transit and ordered 20 with an option for 10 more.

Bombardier based the ALP-45DP on the ALP-46, which was an all-electric locomotive and is closely related to the European TRAXX locomotives. The designation stands for “American Locomotive Passenger”, 4 axles, 5 megawatts, “Dual Power”. All the equipment had to be accommodated in a four-axle locomotive with a maximum axle load of 72,000 pounds anyway. Since the locomotives were only to be used in push-pull trains with cab cars, a second driver's cab was not required.

Like the ALP-46, the power train for electric operation is based on that of the TRAXX 2E, which is used in Germany as class 186 and enables a top speed of 125 mph or 201 km/h. In the ALP-45DP, however, it only delivers 5 megawatts. In order to achieve an output of more than 3,000 kW in diesel operation, the choice fell on two light, fast-running twelve-cylinder engines from Caterpillar, each with its own generator. These are designed in such a way that if one engine fails, the locomotive can still be used with the other. The top speed is limited to 100 mph or 161 km/h in diesel mode.

The power train is designed in such a way that the change between the modes can even take place when running and there is no interruption to the power supply of the train. However, the NJ Transit locomotives were manipulated in such a way that the change can only take place when stopping at a station in order to prevent them from gliding along without power during the 100 seconds required for this. Regardless of the current operating mode, up to 1,000 kW can be diverted to supply the passenger cars, which reduces the power available at the wheel to 2,039 kW in diesel mode.

At NJ Transit, the first delivery replaced the various passenger variants of the EMD GP40. After the first batch, 17 more were ordered in 2017. In 2020, another eight were ordered to replace Alstom's older PL42AC. At Exo, in 2019, the part of the line they traveled in electric mode was integrated into the new driverless metro. They are now only operated in diesel mode.

The class 73 is a dual-power locomotive developed to bridge the non-electrified sections of the third-rail electrified network of the Southern Region. The main reason for their introduction was that large goods yards were not electrified. So the class 73 was mainly used under 630 to 750 Volts DC using retractable contact shoes and could start its diesel engine when needed.

In electric mode, it had an output of 1,600 hp. The diesel engine was a four-cylinder English Electric 4SRKT Mk II with 600 hp. This power was enough to move goods trains around yards at low speeds, but not to run trains on non-electrified mainlines. Even the 1,600 hp available in electric mode was only enough for shorter express trains, since the timetables in the Southern Region were made for four- or five-car EMUs with around 1,000 hp. 

The first six prototypes built in 1962 at Eastleigh were called class 73/0 and had a top speed of 80 mph. 43 more were built between 1965 and 1967 by English Electric at Vulcan Foundry which were called class 73/1 and had a top speed of 90 mph. They are equipped for multiple working with different types of multiple units and locomotives of the Southern Region.

Until 2005, they operated the Gatwick Express with the help of a class 489 Gatwick Luggage Van (GLV) that was a 500-hp driving trailer rebuilt from a class 414 multiple unit. GB Railfreight uses the class 73 mainly for engineering trains. In 2013, three were rebuilt to class 73/9 by replacing the 600 hp diesel with a 1,600 hp V8 built by MTU. Also designated class 73/9 are two rebuilt by Network Rail with two 750 hp Cummins QSK19 each. Several locomotives are preserved, although most preserved railways are not electrified and can only use the class 73 in diesel mode.

For traffic on routes that are not fully electrified, DRS ordered ten dual-powered locomotives from Vossloh España (today Stadler). Under the overhead line, they deliver 4,000 kW and the diesel engine delivers 710 kW, which is more than conventional electric locomotives with last-mile function. They are based on the UKLight, which is in service as class 68 and have 70 percent common parts with it. At first glance, they can only be distinguished visually by the additional pantograph. The engine here is a smaller Caterpillar C27 with only 27 liters displacement from twelve cylinders. DRS remained the only customer of the Class 88. The locomotives are mainly used to pull freight trains, but often also to pull passenger trains.

In the late fifties, Fairbanks-Morse tried to establish a new type of lightweight diesel locomotives for passenger service. Power came from FM's opposed piston diesel engine that delivered 1,600 hp in this case. The prime mover was to be operated at constant RPM, so 400 hp could be used to generate electricity for the train and 1,200 hp were available for traction. The locomotives were optionally offered with contact shoes for operation in non-diesel areas like New York's Grand Central Terminal. The idea was to put one of these locomotives onto each end of a lightweight Talgo train that was to be built in the USA.

The New Haven ordered two for their “John Quincy Adams” train which were classed EDER-7 and got the numbers 3100 and 3101. They had contact shoes, while the two locomotives of the Boston & Maine were diesel-only and numbered 1 and 2. These were used for the train called “Speed Merchant”. The B&M used these units until 1964, but the NH stored their locomotives after a short time and sold their Talgo train to Spain. They were replaced by the EMD FL9 with conventional coaches.

With progressing development, it was possible to modify the Vectron DE into a dual-power locomotive. By reducing the diesel tank from 2,600 to 1,500 liters, a transformer could be accommodated under the locomotive's frame. Together with the pantograph and other electrical equipment on the roof, it is now possible to feed the traction converters from either the overhead line or the diesel generator.

The original Vectron Dual Mode is used as class 248 and has the same engine as the Vectron DE, which has since been discontinued. This means a gross engine power of 2,400 kW and a traction power of 2,000 kW. In electric mode, 2,400 kW are available for traction. The largest operators include the Paribus Group, DB Fernverkehr, ITL and Rheincargo, other locomotives are used in numbers of mostly just one or two locomotives by a whole range of smaller customers.

Since the DM with an axle load of 22.5 tonnes cannot be used on some sidings, the DM Light has been delivered in parallel since 2022 as class 249. In electric mode, the power fell only slightly to 2,210 kW and a Cummins QST 30-L delivers 950 kW, of which 750 kW arrive at the wheel. The result is an axle load of only 21 tonnes. With the DM Light, DB Cargo is replacing part of the former V 90 in shunting operations. Due to the lack of side windows, this got additional microphones and cameras and also shunting platforms, which increase the overall length. After the first series of 100 pieces for DB Cargo, there are still options for more than 200 pieces.

With older electro-diesel locomotives, compromises had to be made between the two types of power, since it was not possible to accommodate two full-fledged power systems. As development progressed, Stadler succeeded in combining an electric locomotive with an output of 7,000 kW and a diesel locomotive with 2,800 kW in one locomotive body. The development was primarily driven by the Havelland Railway, which needed a locomotive for the Rübelandbahn that could also work under 25,000 volts and also provide full traction on the non-electrified connecting lines.

The basis was the Euro4000, which Vossloh manufactured in Valencia, Spain. After the plant was bought by Stadler in 2015, this locomotive could be used as a basis and further developed into a modern dual-power locomotive. The EMD engine was replaced with the more compact Caterpillar C175-16 that Vossloh had already used in the British class 68. In electric operation, the locomotive is compatible with four systems with direct and alternating current. Under 25,000 volts it has an output of 7,000 kW and under 15,000 volts only 6,150 kW. Since there is not such a high level of power available in DC operation, the diesel engine can additionally be used here. The power mode can also be switched while running, but this is not permitted in Germany.

At the same time as the EuroDual, the Euro4001 was developed as a pure diesel locomotive with the same engine. A purely electric locomotive with a maximum of 6,200 kW under 25,000 volts is offered as the Euro6000. The most powerful variant is the Euro9000, which has an output of 9,000 kW when operated with alternating current. The diesel engine is declared here as a last-mile diesel and has an output of only 900 kW. Optionally, however, even two of these engines can be installed.

The EuroDual and the Euro9000 are mainly operated by German railway companies and leasing companies. Seven are used in Turkey and 30 more will be delivered to GB Railfreight in the UK from 2025. Although they are also optionally available for 160 km/h, they are normally only used in freight service. The Euro6000 has so far only been delivered to customers from the Iberian Peninsula, most of them in Iberian broad gauge and some in standard gauge. 

Although nearly all tracks in Switzerland are electrified, there are still a few short sections in yards or in industrial sidings which don't have a catenary. So trains which operated over these short non-electrified parts either needed a diesel locomotive over their full length or the locomotive had to be changed. To overcome this and to reduce its carbon footprint, the SBB ordered an electro-diesel shunter.

Stadler won the tender with their Eem 923 “Butler” that was based on the Ee 922 electric shunter. 30 have been delivered in 2012 and 2013. The power in electric mode was increased to 1,500 kW and a 336 kW diesel engine was added for the non-electrified sections. While its predecessor can only reach 40 km/h when running under its own power, the new locomotive can reach 120 km/h.