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The Caravan is a civilian unit that generates Wealth by traveling a fixed trade route between two particular cities. The gather rate of a Caravan depends on multiple factors including the distance between the cities and the number of buildings built inside each of the cities' economic radius. This gather rate is shown (along with the route) in the unit information box when the Caravan is selected. Only one Caravan may trade between a particular pair of cities.
Setting up a trade route
After a Caravan is created, it first needs to establish its trade route between two cities. This can be done manually by the player by either right-clicking on a city and having the Caravan pick the most favorable second city automatically, or by right-clicking and dragging a line between two cities. However, Caravans will also attempt to set up a trade route automatically, if left idle for some time. This idle time is the same that citizens will wait before looking for something productive to do and it can be set in the game options under Auto-Citizen Delay. While establishing the route, the caravan unit also creates roads.
To complete setting up a trade route, a Caravan must complete an entire loop between two cities involving the following steps:
- Arriving at the first city.
- Arriving at the second city.
- Returning to the first city.
Once a Caravan has completed setting up its trade route by completing an entire loop, the Caravan begins to gather Wealth at a constant rate, continuously traveling between the two cities while doing so. The Caravan's actual movement - including any delays from blocking units etc. - has no effect on the Caravan's income.
With Commerce 3 (Trade) researched, Caravans may also establish trade routes to friendly and allied cities. When this is done, each nation each simultaneously receives the full income from the Caravan - effectively doubling the value of the route. One-time Wealth bonuses for setting up the trade route are given first to the owner of the Caravan (when first arriving at the second city), and then to the other player (when returning to the first city). Each of these bonuses are double what is usually given, and are calculated based on each player's own Commerce level. This means that the single bonus each player receives is equal to what they would normally have received from both bonuses.
To calculate the amount of Caravans you need, simply add all numbers up to the number of cites you have together. For example, if you have 5 cities, you need (4 + 3 + 2 + 1) Caravans. This can be calculated by the following:
Calculating Caravan income
Caravan income is based on several factors:
- The base income for a trade route is 2 Wealth.
- The size of each of the two cities which the Caravan is trading between.
- Each building within the economic radius of either city adds 1 additional Wealth.
- All of the above are added together and multiplied by between 100% (no increase) and 200% (double) depending on the distance between the two cities.
- This multiplier appears to be based on a theoretical straight line drawn between the two cities, ignoring terrian and any other obstructions.
- The multiplier scales smoothly from 100% to 200% as distance increases. For example, one route could receive a 137% multiplier while another, slightly longer route might receive a 182% multiplier.
- Two cities that are as close to, or very close to, the minimum possible distance apart receive the minimum 100% multiplier (no increase).
- Two cities that are fairly far apart from each other receive the maximum 200% multiplier, doubling the income of that trade route. It is not possible to exceed this multiplier by utilising two cities unusually far apart (such as on opposite sides the map) - the multiplier will still only be 200%.
These factors ultimately result in the following equation:
Caravan Income = (2 + (2 * each Large City + 4 * each Major City) + (1 * each building in either city’s economic radius)) * Distance multiplier
- The Chinese Power of Culture: Caravans are created instantly.
- The Indians Power of Majesty: Caravans produce 15% more Wealth.
- The Nubians Power of Trade: Caravan limit is increased by 1. Their Caravans are also cheaper and have +50% hit points.
- The Persians Power of Ceremony: Always have the maximum number of Caravans.
- The Dutch train Armed Caravans instead of Caravan, which is equipped with a light weapon to provide basic defense against raiding attacks. Unlike the Armed Merchant, the Armed Caravan continues to provide its bonus while attacking.