A train simulator (also railroad simulator or railway simulator) is a computer based simulation of rail transport operations. They are generally large complicated software packages modeling a 3D virtual reality world, with ‘play mode’ software which lets the user interact by stepping inside the virtual world. Some, like the first Microsoft Train Simulator are written and modeled for the user mainly interested in driving.
Like flight simulators, train simulators have been produced for railway training purposes. Driver simulators include those produced by:
Ongakukan in Japan
EADS in Germany
Bentley Systems in the UK
Lander Simulation & Training Solutions, Spain 
Transurb Technirail, a Belgian company based in Brussels
CORYS T.E.S.S., a French company based in Grenoble
Krauss-Maffei Wegmann GmbH & Co KG (KMW) www.kmweg.de/, a German company based in Munich
Sydac a member of the Knorr-Bremse Group based in Australia.
OKTAL, a French company member of the international group SOGECLAIR based in Toulouse
New York Air Brake, an American company based in Watertown, NY.
PS Technology, an American company based in Boulder, CO.
Signaller training simulators have been developed by Funkwerk in Germany, The Railway Engineering Company (TRE) in the UK, OpenTrack Railway Technology in Switzerland, and PS Technology in the US
Train driving simulation games usually allow a user to have a “driver’s view” from the locomotive’s cab and operate realistic cab controls such as throttle, brake valve, sand, horn and whistle, lights etc.
One of the first commercially available train simulators was Southern Belle, released in 1985. The game simulated a journey of the Southern Belle steam passenger train from London Victoria to Brighton, while at the same time the player must comply with speed limits, not to go too fast on curves and keep to the schedule. It was followed with Evening Star in 1987.
Other train driving simulation software includes:
BVE Trainsim (originally Boso View Express) is a Japanese three-dimensional computer-based train simulator. It is notable for focusing on providing an accurate driving experience as viewed from inside the cab, rather than creating a network of other trains—There are no outside views, drivers can only look directly ahead, and other trains passed along the route are only displayed as stationary objects.
openBVE, an open source derivative of BVE Trainsim, which although developed from scratch expands upon the capabilities of BVE by including support for train exteriors, animated 3D cab environments and animated scenery.
Trainz, an extensively expandable and user extendable (by scripts) simulator with intuitive GUI world modeling and asset creation facilities, an extensive freeware library of over 250,000 assets, and an attention to Train physics. The simulator offers 4 viewing modes, and for beginning drivers or learning a route, a control mode similar to that of a H.O. scale model train set.
Densha de Go!, a Japanese (only) train simulation game series focused on driving.
Microsoft Train Simulator (MSTS), with limited route building and difficult expansion capabilities.
Open Rails, a free software alternative to MSTS which is functionally equivalent but uses current technology and has an active development programme.
Rail Simulator, another extensively expandable and user orientated creation simulator with intuitive driving modes and editing tools. The main focus is on driving a train from the cab while performing a series of pre-determined tasks. Additional modes allow differing levels of control and interaction. Built by the company behind the original Microsoft Train Simulator software, and published by Electronic Arts.