Simutrans is a freeware and open-source transportation simulation game that runs under Windows, Linux, BeOS on PC, and OS X on Intel based Macs.
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.
You can choose from a large amount of trains including steam, diesel and electric engines, along with multiple units - each with a different properties. Fleet of ships and ferries, buses, trams, trolley buses, trucks, and planes are at your daily disposal. More exotic ways of transport include monorails and maglevs.
Make your own bus system, transporting people throughout the city and lay out new bus routes to make cities grow. Watch your cities really come alive with trucks driving around carrying all kinds of goods. Supply the bookstore with new books and watch out, the Car Seller has almost run out of new cars! Be sure that the furniture factory has enough wood. Oops, the materials wholesaler has just sold his last planks, be quick to buy a new truck to strengthen out that route!
Connect all kinds of industries with each other, the Power Plant needs coal to run. The Refinery gets its supplies from either an Oil Field or an Oil Rig, and produces plastics which allow new cars required by the Car Seller to be built, and gasoline that is sold in gas stations to make those cars run. More of these industry chains are built in this incredible simulation.