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An example of the locomotives typically used on North American long-distance freight trains. CSX locomotives 923 (GE ES44AH) and 169 (GE AC4400CW).

On North American railroads, a wide variety of diesel locomotives are in use for hauling freight and passenger services, with electric locomotives used on some passenger routes, as well as a very small number of isolated freight lines (not represented in FYM). Locomotives are mainly characterized by their horsepower (HP) rating, and can broadly be divided into small (3000 HP and below) and large (above 3000 HP). Smaller locomotives are typically used for switching and local freight services, while larger locomotives haul long distance freights. Locomotives are usually owned by a specific railroad company, and typically remain on their "home" railroad. A small number of locomotive leasing companies also exist, mainly offering services to shortline railroads and industrial switching.


The words locomotive, loco, engine, and unit can be used interchangeably. The term power is used in a more vague sense to refer to a railroad's fleet of locomotives, and it is common to hear a player asking "do you have any spare power?" when they are running low on engines.

Locomotives in FYM

Each locomotive has a Reporting mark, such as UP 1234, indicating the owning company (UP, the Union Pacific railroad) and the locomotive's individual number. In addition, every locomotive is assigned to one of the 200+ locomotive types represented in FYM, which describe the detailed characteristics of that locomotive. These characteristics are:

  • Horsepower (HP): How powerful a locomotive is, often considered in terms of the HP per Ton (HP/T) of a train - a train with a low HP/T will move slowly!
  • Tractive Effort (TE): How much pulling power a locomotive has at low speed. This number is higher for heavy locomotives (more grip), and is also generally higher for more modern locomotive types.
  • Weight
  • Length


Unsurprisingly, diesel locomotives must be fueled regularly. This is usually done at fuel tracks, usually located in locomotive maintenance facilities. On some busy mainline routes, fuel racks are located along the mainline tracks at strategic locations to allow the fast fueling of through trains. (To see a good example of this, look at the run-through fueling tracks BNSF has on the Belen, NM map.) It is also possible to fuel locomotives at remote locations from fuel trucks; this is not simulated in FYM.

In FYM, locomotives are simulated as having a range of 3000 miles between fuel stops. The miles since the last fuel stop is indicated in the "L" column of the Train Information Window, and when hovering over the locomotive with the mouse. Once a locomotive reaches 2500 miles, a warning will be displayed when it enters a map, and it will flash until refueled. If a locomotive exceeds 3000 miles, it runs out of fuel, and no longer provides any power.

Locomotives can be refueled at a Fuel Track, which is colored red. In the Connection Map, yards with fuel facilities are marked with the letter "F". Players should fuel locomotives regularly, especially at major fueling facilities. Some trains will even have notes in the TSAR reminding players to fuel trains, especially if a train is about to embark on a round trip (typical for unit trains) where no fueling facilities will be available until the train returns to that yard. Trains departing from major terminals (for example, BNSF's Galesburg Yard or any Amtrak long-distance terminal) should have their engine fuel topped off before departure.

Unit in Tow (UIT)

In some cases, not all locomotives need to be turned on to haul a train, and disabling these locomotives saves on fuel and maintenance. Common examples are coal or grain trains, which require all locomotives when loaded but not when empty, and transfers of locomotives from one yard to another.

This feature is present in FYM. In the Train Information Window, a locomotive can be set "In Tow" by selecting it and pressing the "UiT" button. When this is done, "Unit in Tow" will be displayed at the end of the locomotive's entry, and it will provide no power to the train, and no fuel will be used. Such units are also indicated when hovering over them with the mouse in the map.

If you load a coal, grain, or other unit train, make sure to turn on all locomotives before the train leaves. This is done in the same way as before - select it in the Train Information Window, and press "UIT".

Engines that are UIT are not free for the taking. "Sniping" UIT engines is discouraged, especially from unit trains that rely on the power after the train gets reloaded. If power is being shuttled on a regular train to another yard, the originating yard master should put notes in the Train Information Window to make sure other yard masters know about the power transfer. Likewise, a note can be added to let other yard masters know that the extra power is free for the taking by anyone along the way.

Bad Order (BO)

A locomotive that is damaged and marked Bad Order must be repaired at a Repair Track before it can provide any power. Locomotives are only bad ordered when they are in a collision.

Locomotive types in detail

IHB 1509, an EMD SW1500, used for switching and local trains.

The North American locomotive market has been dominated by two manufacturers, EMD and GE, since the end of the 1960s. An overview of the locomotives from these manufacturers, and others, is given below.


Electro-Motive Diesel (EMD), formerly the Electro-Motive Division of General Motors, has been producing diesel locomotives since the 1930s. The company's products are usually prefixed by two letters followed by several digits and letters, such as SW1500, MP15DC, GP38, or SD70MAC.


The EMD SW (SWitcher) series consists of small locomotives rated at 1500 HP or below, with models built from 1939 until the mid 1970s. The MP (Multi Purpose) series extends this to the mid 1980s. As suggested by the "switcher" designation, these locomotives are mainly used for switching duty in yards or industries. The more powerful SW variants and the MP15DC/AC/T types are still in use on Class I railroads, but in dwindling numbers. However, SW locomotives of all types are very commonly found on private industrial switching duties at grain elevators, steel mills, and chemical plants.

Early GP and SD locomotives

BNSF EMD GP38-2s 2088 and 2349, used for local and medium distance services.

The GP (General Purpose) and SD (Special Duty) locomotive families evolved in parallel, with the GP locomotives having 4 axles, while SD units have 6 axles. The early GP7 and GP9 units were incredibly popular, and are commonly found on shortlines and in industrial duties. The GP38 (2000 HP), GP40 (3000 HP), and SD40 (3000 HP) units were similarly popular products, in addition to their "Dash-2" upgrades (GP38-2, GP40-2, SD40-2). These are still present in large numbers on Class I railroads, carrying out most switching and short distance freight work. A large variety of specialized, modified, altered, or upgraded types of these locomotives exist, but their characteristics are broadly similar. Developments into the 1980s and 1990s brought some units above 3000 HP, such as GP60, SD50, and SD60; these can also be found on Class I railroads.

Later SD locomotives

KCS 4056, a modern EMD SD70ACe locomotive, used to haul heavy, long distance trains.

In the 1990s, the SD60 and SD70 lines provided more powerful locomotives with around 4000 HP, which form the modern mainline fleets of Class I railroads, in addition to GE's competing products. A major change was the introduction of AC traction motors to some models, which led to large increases in the available tractive effort. The more powerful SD80MAC and SD90MAC units did not prove popular with railroads, with the SD90MAC suffering badly from reliability issues.


The General Electric (GE) company has been involved in diesel locomotive manufacture since the late 1930s, but until the last few decades, it did relatively poorly in the North American market, mainly selling its products overseas. Its Dash-8 and Dash-9 lines cemented its place as a provider of mainline locomotives, and it has continued in that role to this day.


Early GE switchers are only found in industrial switching. These are mainly referred to by their weight, with the 44-Ton and 77-Ton variants being most common.

Universal Series

Despite having been comparable with EMD products such as the SD40-2, GE's Universal Series (e.g. U18B) are no longer well represented in North American railroad locomotive fleets, even on shortlines. However, they are still commonly found overseas.

Dash 8, Dash 9, AC, and Evolution series

CN 2839 and 2854, modern GE ES44AC locomotives, hauling an intermodal train.

GE's Dash 8 locomotives, introduced in the late 1980s and early 1990s, were reasonably successful, and can still be found in mainline use. The Dash 9 series offered upgraded electronics and trucks from the mid 1990s, and were hugely successful compared to older GE models. AC traction motors were first provided with the AC4400CW and AC6000CW models, with the latter proving more reliable than EMD's competing 6000 HP product, the SD90MAC. Further upgraded models with both DC and AC traction motors were grouped into the Evolution series, such as the ES44AC and ES44DC. The ES44C4 units are similar to the ES44AC, but only four of the six axles are powered; these are typically used on fast, light intermodal trains. GE's latest offerings are the ET44AC and ET44C4, upgraded versions that are compliant with modern air pollution laws (EPA Tier 4).


The American Locomotive Company (ALCO) and its Canadian subsidiary, the Montreal Locomotive Works (MLW), was a major force in locomotives until the end of the 1960s, producing a large number of both steam and diesel locomotives. However, ALCO produced its last locomotive in 1969, following the collapse of its partnership with GE in 1953. Very few of ALCO's main line locomotives, the Century series (e.g. the ALCO C424), remain in service. A slightly larger number of its Roadswitchers (RS-) and Switchers (S-) remain in use on shortline railroads and industrial locomotives.

Modern switcher manufacturers

UPY 2315, a modern RailPower GG20B switching locomotive. Uptake of newer switching locomotives remains low.

In the 21st century, a number of companies have begun offering either rebuilt or newly built switchers, as both GE and EMD are almost entirely focused on sales of large, mainline locomotives. These new units offer better fuel efficiency and reduced emissions, with several models incorporating battery technology and multiple separate diesel engines that can be turned on only when required. Such manufacturers include MotivePower Inc. (MPI), National Rail Equipment (NRE), Progress Rail, and Railpower Technologies (RP).

Whilst a number of these locomotives have been purchased by both large and small railroads, they are still generally outnumbered by much older switching locomotives.

Distributed Power Units (DPU)

Creating trains with distributed power (DP), (multiple engine consists; DPU) calls for some additional attention to detail that will help make them more realistic for your neighbors. In the familiar, multiple-unit (MU) head-end consists, the engineer controls all units at the same time via MU cables that connect the lead, controlling unit to the trailing units. DP is similar, but instead of cables, DP works by radio communication. Nearly all engines are equipped with MU; the main exceptions being industrial switchers that never work in multiple-unit consists. The same is not true for DP controllers, so many engines today cannot be controlled by radio.

Here are some key points for correct DP operation:

  1. Lead engines must be DP equipped, as must at least one engine in each DP consist.
    The engineer of a DP train must be operating an equipped engine, and the radio link is between that lead and one engine in each trailing consist. Other engines in consists are controlled by MU, so they do not need to be equipped with DP radios.
  2. DP consists cannot be too far apart.
    If radio communication is lost between the lead engine and DP consists, bad things can happen. Also, in-train forces can be tricky for long trains. For these reasons, railroads limit the distance between DP consists, and for longer trains, this means DPUs must be cut in the middle of the train. The distances vary by railroad. Currently BNSF and UP are 8500 feet and CSX is 7000 feet, though in contrast, CN has been observed to allow very long distances between DPU units on intermodal trains, up to 200 well cars (~11-12,000ft).
    For very long or heavy trains, multiple DP consists can be used. The distance limits noted above will then apply to the distance between each adjacent pair, although it is very rare for a train to be so long that the distance limits can be exceeded multiple times.
  3. The linked engine in every consist must be online.
    The lead engine must be powered, and so must at least the linked controlling unit for any trailing consists. For empty unit trains, this means that often there are two engines online: the lead and one in the DP consist. In-train rain forces are severe because engines are very heavy, so all engines cannot be offline in any consist.
  4. Up to three remote DP consists may be controlled by the lead unit.
    Especially on BNSF and UP, it is common to configure trains with both mid-train and rear-end consists. Only a few trains, mostly experimental or special moves, have used all four consists available.

Finer points for zen masters:

  1. There are multiple versions of DP radio systems and software, and some are not inter-operable. For this reason, DP trains tend not to have foreign units, or at least not in the lead. There are exceptions and the situation changes over time.
  2. To avoid derailments due to high forces near pusher consists, most railroads require DPUs to shove on loaded cars in mixed trains of loads and empties.

Which engines are equipped with DP radios?

BNSF Most SD70MAC, most Dash 9 except older units, ES44DC, all other AC engines
UP All AC units (a few older exceptions), 9300 C40-8. Notably not Dash 9-44CW, SD70M, or SD60M
NS All AC units, ES44DC 7557-7616 and 7670-7719, Dash 9-44CW 9212-9229
CN All AC units, ES44DC, SD70M-2, Some Dash 8s and Dash 9s, Notably not SD75
CP All AC units
KCS All AC units (excluding SD70MAC which are all retired now)