Simutrans, 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 air. Interconnect cities, districts, public buildings, industries and tourist attractions by buiding a transport network you always dreamed of.

You can control and watch your finances and the traffic of your vehicles and goods. Play as long as you like. Start in 1880 and finish in 2050. There will be new vehicles and buildings throughout this time. Cities will grow and merge forming metropolises.

Play against the AI or on your own. Only if you are in debt for three months, you are bankrupt and the game is over.

Official Website: http://simutrans.com/

Another open-source game that should consider in, please come to the official website of the game and try to play it.