A trade route is established when a caravan or freight travels from one city to another; a permanent trade boost is established, varying in size with factors such as distance and whether the cities are on the same continents or in the same empire. Maximum three per city. As a result, new trade routes added to or from cities with three pre-existing routes may either replace one of those routes or be superseded by existing routes. In the event of the latter, this means that extra caravans / freight will produce either just a cash payout or fill the recipient city’s food storage if it is a food caravan.
Trade units may also transfer food from one city to another rather than creating a trade route, or contribute all of their production points to building a wonder.
Trade routes are established by moving a Caravan or Freight unit into a city at least ten squares from the unit's home city. You receive an immediate cash payment on the turn that the route is established. On each ensuing turn, each city receives a Trade bonus for as long as the trade route exists. The farther apart the two cities are, the more valuable the trade route. Trade routes established with cities of a rival civilization tend to be more profitable than those established between friendly cities. Each city may have up to three active trade routes at any time.
The value of a trade route is also affected by the type of goods traded. When trading a commodity that is demanded by the destination city, the trade route is much more profitable.
- Main article: Commodity (Civ2)
- The math behind trade route income 
|Civilization II |
|Conflicts in Civilization • Fantastic Worlds • Test of Time†|
Attitude (Civil disorder, We Love the King Day) • City (Capital) • Combat • Difficulty level • Espionage • Food • Gold • High Council • Luxuries • Odeo year • Pollution • Production • Reputation • Science • Spaceship • Specialists • Tax Rate • Trade • Trade route
|† Standalone remake with different graphics, units, etc|