Simutrans is a transport and economic simulation which contains some ecological aspects as well. The goal of the game is to build an infrastructure which allows to transport goods between the various industries and towns. A second goal is to become as rich as possible, but you'll have to reinvest a good amount of your earned cash to expand your infrastructural network. Your competitors won't sleep!
After the simulation has started, there are only few cities and industries on the map with no infrastructure between them. Now it's on you and your competitors to build roads and railroads, and deliver goods and drive passengers where they need to go.