Simutrans is a free and open-source transportation simulation game.

In Simutrans you can build the transport networks you always dreamed of, with platforms, quays, level crossings, bridges, tunnels, signals and much more. Transport passengers between nearby cities with a commuter train or use a high speed train to earn big money by connecting cities further apart.

http://repo.openpandora.org/?page=detail&app=simutrans