Electro-diesel locomotive

An electro-diesel locomotive (also referred to as a dual-mode or bi-mode locomotive) is a type of locomotive that can be powered either from an electricity supply (like an electric locomotive) or by using the onboard diesel engine (like a diesel-electric locomotive). For the most part, these locomotives are built to serve regional, niche markets with a very specific purpose.

Overview
Electro-diesel locomotives are used to provide continuous journeys along routes that are only partly electrified without a change of locomotive, avoid extensive running of diesel under overhead electrical wires and giving a solution where diesel engines are banned. They may be designed or adapted mainly for electric use, mainly for diesel use or to work well as either electric or diesel.

Note that, as well as the electric multiple unit (EMU) and diesel multiple unit (DMU), where no discrete locomotive is present, an electro-diesel (bi-mode) multiple unit train is called electro-diesel multiple unit (EDMU) or bi-mode multiple unit (BMU).

Primarily electric
This is effectively an electric locomotive with a relatively small auxiliary diesel prime mover intended only for low-speed or short-distance operation (e.g. British Rail Class 73). Some of these, such as the British Rail Class 74, were converted from electric locomotives. The Southern Region of British Railways used these locomotives to cross non-electrified gaps and to haul boat trains that used tramways at the ports of Southampton and Weymouth. For economy, the diesel engine and its generator are considerably smaller than the electric capacity. The Southern types were of 1600 hp or 'Type 3' rating as electrics, but only 600 hp as diesels. Later classes had as much as 2500 hp on electric power, but still the same diesel engines. Despite this large difference, their comparable tractive efforts were much closer (around three-quarters as diesels) and so they could start and work equally heavy trains as diesels, but not to the same speeds.

From 2010, in continental Europe, the name "Last mile diesel" was getting popular. These are electric locomotives with a small diesel engine of truck type, used in low speed, low gear, for operation at small flat freight yards, eliminating the need for a shunter locomotive.

Primarily diesel
This is effectively a diesel locomotive with auxiliary electric motors (or connections to the existing traction motors), usually operating from 750 V DC third rail where non-electric traction is banned (e.g. EMD FL9, GE Genesis P32AC-DM, EMD DM30AC). The primary function for these models is to provide a "one-seat ride" (a rail trip that does not require a transfer to a different train) between the electrified and non-electrified sections of a rail system or to allow trains to run through tunnels or other segments of track where diesel locomotives are generally prohibited due to their production of exhaust; such locomotives are used for certain trains servicing the New York City terminals of Grand Central Terminal and Penn Station, as the various rail tunnels into Manhattan have exhaust restrictions. Once out of the tunnels, the engines are started and operation is as a normal diesel locomotive.

Full dual-mode
With modern electronics, it is much easier to construct (or adapt) an electro-diesel locomotive or multiple-unit which is equally at home running at high speeds both "under the wires" and under diesel power (e.g. British Rail Class 88, Bombardier ALP-45DP). These will normally operate under pure electric traction where possible, and use the diesel engines to extend the journeys along non-electrified sections which would not be cost effective to electrify. They may also be used on long cross-country routes to take advantage of shorter sections of electrified main lines.

Georgia
ETG, an experimental electro-diesel shunter converted at Tbilisi locomotive depot in 1967 from AMG5 diesel-hydraulic shunting locomotive (manufactured by Gratz, Austria) by replacing its diesel prime mover with less powerful diesel engine and two electric motors from VL22m locomotive. The locomotive operated for several years and was withdrawn in the 1970s.

Germany

 * Gmeinder class 478.6 diesel and 750 V DC third-rail (bottom contact).
 * Voith Futura, a 2009 CREAM Project concept locomotive rebuilt from DB 240 002.
 * Bombardier TRAXX "Last Mile Diesel", mainly electric. Orders signed 2010, to be delivered probably 2012.
 * Siemens Vectron Dual Mode

Poland

 * Pesa 111Ed Gama Marathon – mainly electric, with auxiliary diesel engine enabling last-mile operation on non-electrified tracks. Gama Marathon was first presented in 2012 at InnoTrans Berlin. The locomotive then underwent a series of tests with rail operators Lotos Kolej (in goods traffic) and PKP Intercity (in passenger traffic), after successful conclusion it was offered on the market. In July 2015 the Polish train-operating company Locomotiv bought the prototype and signed order for further two Marathons.
 * Newag Dragon – version of this electric freight locomotive for the Freightliner's Polish branch, Freightliner PL Sp. z o.o. (five units delivered in 2016) is equipped with auxiliary diesel engine.
 * Newag Griffin – a version of this electric freight locomotive, leased to Lotos Kolej in 2017 for 7 years with a provision to extend the lease, is equipped with auxiliary diesel engine.

Russia
In Russia, a number of electro-diesels were built which had both pantographs and diesel prime movers. These included:


 * ED16 (ЭД16), ED18 (ЭД18), and TEU1 (ТЭУ1) experimental narrow gauge models for 750 mm gauge railways with 6 kV 50 Hz AC overhead wires, produced by Demikhovo Machinebuilding Plant
 * OPE1 (ОПЭ1 ), full dual-mode freight locomotives, used mostly in quarries and some another industrial railways with 10 kV 50 Hz AC overhead wires, produced by Novocherkassk Electric Locomotive Plant. Each locomotive consists of two sections with dedicated electric and diesel power equipment, which can operate as a standalone single-ended electric or diesel locomotives, some of them are also equipped with a motorized dump car.
 * OPE1A (ОПЭ1А ), OPE1B (ОПЭ1Б) and PE3T (ПЭ3Т), full dual-mode freight steeplecab locomotives for quarry railways with overhead wires with 10 kV 50 Hz AC electrification (OPE1A/B) or 1.5 / 3 kV DC (PE3T), produced by Dnipro Electric Locomotive Plant, Ukraine. A complete locomotive consists of primary electric A unit with a cab, one diesel-electric B-unit with a lowered body and one motorized dump car, however most OPE1A locomotives were produced without diesel B-units and with two motorized dump cars.
 * LEW EL10 EL20, mainly electric locomotives for quarry railways with 10 kV 50 Hz AC overhead wires. Each locomotive is equipped with two motorized dump cars.
 * 2EV120, mainly electric two-unit freight locomotive, produced by Engels Locomotive Plant and derived from Bombardier TRAXX. Locomotive using both 3 kV DC and 25 kV 50 Hz overhead wires and can be equipped with auxiliary "Last Mile Diesel".


 * Warnings: the sections below are WORK IN PROGRESS, result of moving to "Electro-diesel multiple unit" the informations about Electro-diesel Multiple Unit, here incorrectly reported; please give help on this transfer.

Spain

 * FEVE 1.900 Series, 1500 V DC overhead wires. This series is a rebuild of FEVE 1.000 Series locomotive.
 * Euskotren TD2000 series, 1500 V DC overhead wires. This is a new construction locomotive. Built by CFD-Bagnères and Ingeteam.
 * CAF Bitrac 3600, 3000 V DC overhead wires. October 2007 order for nine freight Co-Co locomotives. Available in Bo-Bo and Co-Co wheel configuration, 1435 or gauge, and as freight or passenger versions of 120 and 180 km/h maximum speeds respectively.
 * Power cars for RENFE Class 730, by Talgo.

Switzerland

 * Rhaetian Railway Gem 4/4 801 and 802, 1000 V DC overhead wires (Bernina Railway)
 * Swiss Federal Railways Tem I 251–275 (1950–57), Tem II 276–298 (1967) and Tem III 321–365 (1954–62) shunters (Tem III see image) of which only few are still in service.
 * Swiss Federal Railways Eem 923 shunters using both 15 kV 16.7 Hz and 25 kV 50 Hz overhead wires and a 360 kW auxiliary diesel engine are on delivery from Stadler Rail's Winterthur plant.

United Kingdom
An experimental electro-diesel locomotive, DEL120, was built by London Underground in 1940 but was not a success. Two types have been built whose electricity source was a 750V DC third rail.


 * British Rail Class 73, dating from 1962 – the more successful design, with some still in regular use. They originally had lower power output in the diesel mode, but are re-engined to provide more power. (2020, 62 years since introduction)
 * British Rail Class 74 – rebuilt from British Rail Class 71 electric locomotives in 1967 and withdrawn by 1977.

Electro-diesel locomotives whose electricity source is 25 kV 50 Hz AC overhead line include:
 * British Rail Class 88 – locomotive used by Direct Rail Services. Introduced in 2017.

Canada

 * Bombardier ALP-45DP – 20 locomotives ordered for the Mascouche line (Exo) in a joint order with NJ Transit. They provide a through journey on this mostly unelectrified new line, which joins the existing electrified Deux-Montagnes line to access Montreal's Central Station through the poorly ventilated, 25 kV AC electric only Mount Royal Tunnel. With the conversion of the Deux-Montagnes line into the mainline of the Réseau express métropolitain light metro system and the permanent truncation of the Mascouche line to Ahuntsic station starting in January 2020, the ALP-45DPs will be run exclusively in diesel mode.

United States
Several, primarily diesel locomotive types and a multiple-unit have been built to operate off a 750 V DC third rail into the New York City terminals of Grand Central Terminal and Penn Station (with the third rail system being rarely used on open-air tracks).

The following are in service:
 * P32AC-DM – dual-mode version of GE Genesis, primarily diesel, electric mode is only used for service to Grand Central Terminal from Poughkeepsie or Wassaic, or Penn Station from Albany, Rutland, or Niagara Falls. They are also used on the Albany-New York section of trains between Penn Station and Chicago, Montreal, and Toronto. Those trains stop in Albany to switch to full diesel GE Genesis for the remainder of the journey.
 * EMD DM30AC – specific to Long Island Rail Road, primary diesel, electric mode is only used for service to Penn Station.
 * Bombardier ALP-45DP – 35 locomotives purchased by NJ Transit (with 17 more on order), to bridge gaps between non-electrified and electrified sections of track into New York Penn Station. These trains have been used to provide a "one-seat ride" to New York Penn Station for commuters using non-electrified portions of the system.

The following were retired from New York City service:
 * Baldwin RP-210 – primarily diesel-hydraulic, third-rail electric mode for short-term use only. All scrapped.
 * Fairbanks Morse P-12-42 – primarily diesel-electric, third-rail electric mode for short-term use only. All scrapped.
 * EMD FL9 – primarily diesel-electric, third-rail electric mode for short-term use only. Several examples preserved and/or in service on heritage railroads.
 * GE three-power boxcab – tri-mode switcher locomotive model built in 1930, was also capable of operating as a battery locomotive. All retired and scrapped.

South Africa

 * The South African Class 38-000 is a 3 kV DC electro-diesel locomotive designed by Consortium under the leadership of Siemens and built by Union Carriage and Wagon (UCW) in Nigel, Gauteng, South Africa. Between November 1992 and 1993 fifty of these locomotives were placed in service by Spoornet, formerly the South African Railways (SAR) and later renamed Transnet Freight Rail (TFR). The diesel engine enables the locomotive to shunt on unelectrified sidings.

Tanzania

 * Stadler Euro Dual, proposed 25 kV 50 Hz AC overhead wires (Tanzania Standard Gauge Railway)

India
The Indian Railways WDAP-5 is a class of Electro-diesel locomotive that was developed in 2019 by Banaras Locomotive Works (BLW), Varanasi for Indian Railways. The model name stands for broad gauge (W), Diesel (D), AC Current (A), Passenger (P) and 5000 Horsepower(5). The locomotive can deliver 5000HP in electric mode and 4500HP in diesel mode. It was made to reduce the travel time of passenger trains which needed to change the electric locomotive with a diesel locomotive. However as of 2024, this locomotive does not have much practical use as 97% of Indian Railways has been electified. Only one of these were ever constructed and what happened to that locomotive remains unknown.

Hybrid locomotive


A specialized type of electro-diesel locomotive is the hybrid locomotive. Here, the electricity comes from a battery charged by the diesel engine rather than from an external supply. An example is the Green Goat switcher GG20B by Railpower Technologies, a subsidiary of R.J. Corman Railroad Group since 2009.