Baldwin offered gasoline-powered switchers that looked a lot like steam locomotives. They were mainly used for light switching service and, compared to a steam locomotive, had the advantage that they did not consume any fuel during waiting times and could be started again immediately if necessary. One example was in service with the Georgia Coast & Piedmont Railroad and was numbered 99.

The motor was installed together with most of the machinery in the place where the boiler was on steam locomotives. On top of the hood sat the tank and the exhaust, the latter occupying the same space as the chimney. The transmission took place via a two-stage gearbox onto a jackshaft, which drove the wheels via coupling rods. In contrast to most cars of the time, there was already an electric starter for starting the engine, which was operated by a battery, which in turn was charged by an alternator.

With the two gear stages, the locomotive could reach a speed of 6 or 12 mph. In high gear, the locomotive could haul 30 short tons up a 0.5 percent incline, negotiating curves with a radius of 90 feet. 

In search of more powerful diesel locomotives, the Denver & Rio Grande Western ordered three ML 4000 from Krauss-Maffei in Germany in 1961. With hydraulic power transmission and two high-speed Maybach engines with 2,000 hp each, their basic technical concept was completely different than that of American locomotives. The advantages lay in the better power-to-weight ratio and better traction properties of the three-converter transmission. In order to cover the development costs, Southern Pacific was persuaded to order three more ML 4000.

The operators' route network included passes in the high mountains over which trains weighing more than 10,000 tons had to be pulled. The problem turned out to be that the engines were designed for a full load share of ten percent according to German conditions. In the USA, however, this proportion is many times higher, which, in conjunction with the sometimes hot climate, led to problems. In addition, maintenance was found to be too complex compared to the much simpler American locomotives.

The problems were initially so serious only at the DRGW that its three locomotives were sold to the SP, while the SP ordered a second batch of 15 locomotives. While the first batch had a self-supporting car body, the second batch was built in the same way as American road switchers with a supporting frame and machinery covered by hoods. At the same time, the Brazilian Estrada de Ferro Vitória a Minas (EFVM) ordered 16 ML 4000 in meter gauge. 

Southern Pacific No. 9011 in August 1964 at San Jose, California

Drew Jacksich

Although the SP was initially happy with the ML 4000, problems with the air intake in the long tunnels of the Sierra Nevada soon became known. For the same reason, EMD developed some locomotives with modified airflow, which became known as “Tunnel Motors”. When the maintenance of the engines became too expensive, the locomotives were retired by 1968 with the conclusion that the hydraulic power transmission itself was reliable and economical. The 9113 was converted into a camera car in 1969 and is now owned by the California State Railroad Museum. The Brazilian machines, on the other hand, remained in use until the 1980s.

After the Second World War, Lima also tried to catch up with the production of diesel locomotives. A total of 136 switchers were delivered between 1949 and 1951, which received the model numbers A-3149, A-3171, A-3080 and A-3170. They are better known among railroad fans according to their power output under the designations LS-750, 800, 1000 and 1200. Hamilton diesel engines were used, which had six cylinders in the two weaker variants and eight cylinders in the more powerful ones. The generator and traction motors were from Westinghouse. However, these locomotives could not manage to assert themselves against the competitors.

Motive Power, Inc., as the successor company to Morrison-Knudsen or MK Rail, offered a range of passenger diesel locomotives from 2003 that were intended for commuter service. These were four-axle diesel-electric locomotives with a streamlined head shape on one end. Initially, power was provided by the sixteen-cylinder two-stroke engine from the 645 series from EMD with 3,600 hp. 

The first two models were the MP36PH-3S and MP36PH-3C. With the 3S, the power supply for the passenger cars was provided by a static inverter, which made it necessary for the diesel engine to run constantly at nominal speed to provide the required frequency. When calling up the maximum 500 kW, the power available to the traction motors was reduced by this value. The 3C used an additional Caterpillar C27, which provided power for the train independently of the main diesel. From 2015, all Type 3S engines have been upgraded to the same level as the 3C to reduce stationary noise and fuel consumption.

SunRail MP32PH-Q in October 2016 at the Sand Lake Road station

Meloaraujo

From 2007 the MP40PH-3C was delivered, which got a newer EMD engine of the 710 series, which provided 4,000 hp. Here, too, an additional diesel engine was used to supply the train. From 2013 the MP32PH-Q was manufactured, which resulted from the conversion of existing EMD GP40WH-2 and differs from the other models in that the hoods around the prime mover were unchanged and only the head got a new shape. Despite the 32 in the name, the existing engines were upgraded from 3,000 to 3,600 hp. 

Since the new registration of locomotives with the EMD two-stroke engine was no longer possible with the EPA Tier 4 emissions standard coming into effect in the USA on January 1, 2015, production of the locomotives with these engines ended. Now MPI offered the MP54AC with two 2,700 hp Cummins QSK60, which meet the new emissions standard and have an AC drive system. To reduce fuel consumption and emissions, one of the engines can be switched off as needed, making the MP54AC a genset loco.

The largest number is made up of the MP36PH-3C, of which just over 100 were built. It went to a total of nine commuter companies in the USA. Twenty-seven examples of the similar -3S were built for Metra in the Chicago area. Of the MP40PH-3C, most of the 71 examples went to the Canadian GO Transit, as did all 26 examples of the MP54AC. The first MP54AC was created by converting a GO Transit MP40PH-3C accordingly. Only eleven examples of the MP32PH-Q were built for SunRail in the Orlando, Florida area. Most of these had been converted from former MARC (Maryland Area Rail Commuter) GP40WH-2s.

The MP8AC-3 is a diesel-electric locomotive built by MotivePower, Inc for the New York City subway. Right from the basic concept, it was developed as a work train locomotive for this operator. The model name here stands for 800 hp and AC drive.

Since the third rail is generally switched off during work, an electric drive was completely dispensed with. Instead, in addition to the 800 hp main diesel, a second, smaller one is used, which is used to generate electricity when stationary. The bogies are the same from Kawasaki as on the R160 class subway trains and use the same three-phase traction motors from Siemens.

In 2005, NRE used an older diesel locomotive for the first time to rebuild it as a multi-engine genset locomotive. The base was a Southern Pacific EMD MP15DC, originally built as a GP30. Instead of the 1,500 hp EMD 12-645E, two Cummins QSK19C, each with 700 hp, were used, both of which had their own generators. The driver's cab was here in the middle between the engines.

The type was called 2GS14B, which consists of two engines, “Gen Set”, 1,400 hp and wheel arrangement B-B. Other examples of this type have since been built on the basis of different four-axle road switchers, some of which had already been rebuilt. In most cases the cab stayed at one end of the locomotive. Other types with one to three engines soon emerged. Since then, other manufacturers, not only in the USA, have also been offering genset locomotives.

The most powerful design among NRE's multi-engine “N-ViroMotive” genset locomotives is the 2GS36C-DE. Its name stands for two engines with a total of 3,600 hp and three axles per bogie. Power comes from two Cummins QSK50L, each with 16 cylinders and 1,800 hp. The prototype was built in August 2011 on the frame of an EMD SD40-2. Since no further orders have followed and NRE's locomotives with the smaller QSK19 were more successful, only one prototype remained.