Simutrans

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

Your goal is to establish a successful transport company. Transport passengers, mail and goods by rail, road, ship, and even air. Interconnect districts, cities, public buildings, industries and tourist attractions by buiding a transport network you always dreamed of.

Planes, ships, trains, trams, trucks, busses and monorails are at your disposal. You can control and watch your finances and the traffic of your vehicles and goods.

Simutrans is not bound to specific scenario data. Each ’so called’ pakset contains landscape, building and vehicle graphics, creating a world of its own. Therefore each set is like a different game within the simutrans graphics/simulation engine.

http://www.simutrans.com