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. Passengers need transport to and from work, between cities, and to tourists attractions. Raw materials need to be transported to factories, where they can be refined and later delivered to the consumers in the city.
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. You need to keep your bank balance in the positive, or you won’t be in business for long. Your competitors won’t sleep!
Initially, when the simulation starts, there are only few cities and industries on the map with almost 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.