Locomotive

A locomotive (also known as a train engine) is a type of railroad vehicle, examples of which can be found throughout both the Mojave Wasteland and The Commonwealth.

Overview
Very little is known about railroad operations in the Fallout universe prior to the Great War. The presence of freight cars in railyards throughout the wasteland suggests that railroads were used for transporting freight in the pre-war United States.

Fallout: New Vegas
The locomotives appear to belong to the same railroad company, as they are all decorated in the same paint scheme. While an operational example cannot be found in the game, Chomps Lewis at Sloan will tell the Courier that what they dig from their quarry is shipped off by train to the New Vegas Strip and other parts of the Mojave Wasteland.

Fallout 4
These locomotives were used to haul trains - cargo trains exclusively as one conclude from the absence of passenger carriages - until the Great War. By a very long shot, these monstrous machines are the largest ground vehicles appearing in the game, being the height of about a two-story building. Their design is loosely based on a heavy steam engine, with a 6-8-4 ("oooOOOOoo") wheel arrangement. The locomotive has a massive cow catcher on the front made of two huge blades. This is a rather odd design as rather than push dead animals off the track, it would likely rip them to shreds. The engine is also likely very prone to derailing as it is almost two stories tall and has a fairy narrow wheelbase.

Fallout: New Vegas
Train engines can be found on the rail lines around New Vegas. Two examples include a lone engine sitting outside of the entrance to Boulder City, and one attached to several boxcars in the Gypsum train yard.

Appearances
Locomotives appear in Fallout: New Vegas and Fallout 4

Behind The Scenes

 * Locomotives in the Fallout series are based, at least in part, on real-world locomotive design. The locomotives in the Mojave Wasteland are very similar in appearance to the iconic F-Unit series of locomotives manufactured between 1939 and 1960 by the Electric-Motive Division of General Motors corporation. The locomotives in the Commonwealth appear to be inspired by the T1 Class and S2 Class locomotives of the Pennsylvania Railroad, manufactured between 1942 and 1946.
 * The locomotive at the entrance to Boulder City is adorned with the logo for the fictional "Barstow Strong Express". This may be a reference to William Barstow Strong (1837–1914), former president of the real world "Atchison, Topeka & Santa Fe Railway".
 * It is unknown as to how these vehicles were powered. While the real-world F-series and T1 class locomotives were diesel-electric and steam-powered, respectively, the pre-war oil crisis and lack of a coal tender on Fallout 4 locomotive suggest that they may be powered via alternative means.