Vanilla Civilization V and Gods & Kings Trade Routes
A Trade route is a link formed between a civilization's cities and its Capital, which traders regularly use to move and conduct their trading. This might happen via land, using roads, railroads, or via sea, using Harbors. A Trade route is open with a city if one of the above-mentioned infrastructures is in place at the beginning of your turn.
Trade routes can be formed even if the connection is not direct. For example, if the Capital has established a connection to City A via a Harbor, and City A is connected to City B using roads, then both cities are connected to the Capital. As long as there is a transport chain ending in the Capital, a Trade route is opened and functional.
Note that for the Capital to be accessible by sea, it needs either a Harbor built in it, or it needs a road/railroad connection to another city with a Harbor. So, for example, a connection won't be formed if the peripheral cities have Harbors, but the Capital itself has no sea access.
If an enemy pillages a road or uses ships to blockade a coastal city and there are no other connections to the Capital, the Trade routes will be lost until the roads are repaired or the ships leave or are destroyed.
Once formed, Trade routes earn certain amount of Gold for the civilization. Every tile with a road or railroad costs Gold per turn, meaning not all Trade routes are necessarily profitable. The Gold output for any Trade route between a Capital and a city is:
Brave New World Trade Routes
- Main article: International trade route (Civ5)
In this expansion pack, trading has been redefined by introducing a new type of trade routes: International Trade routes. Traditional trade routes between your own cities still exist, but have been renamed City connections, and function the same way as before. We can also think of them now as "Domestic Trading," done automatically as soon as you establish an infrastructural connection between a city and your Capital.
The new type of trade routes may be labeled " International Trade" and are established manually - not only within your own civilization, but also with other civilizations or even city-states. Since in Brave New World Gold production from terrain is significantly reduced, the new trade routes become vital for maintaining your finances. Because of the complexity of the new system, it enjoys a separate article.