Trade represents income generated by ships equipped with trade modules, such as freighters. In order to establish a trade route, a trade module equipped ship must move to a planet belonging to another civilization. The value of the trade route is proportional to the length of the route, as well as the population of both the destination and home planet of the trade ship. Once the trade ship reaches the destination planet, the trade route will be established (represented by a faint trail on the main map and a tiny trade ship traveling on it 1 square per game turn), and both civilizations will start receiving the same base amount of trade income. The base income returned each turn by the route is about proportional to the time the trade ship is en-route, modified by civilization's trade bonus