This paper presents an algorithm to calculate the amount of science and gold received when a caravan establishes a trade route with another city. The algorithm is divided into two sections, the basic formula and multipliers.

Roundown ((BTA of SC + BTA of DC + 1) * (D +10) * FD / 48.5)

• BTA = Base Trade Arrows
• SC = Source City
• DC = Destination City
• D = Distance
• FD = Foreign Delivery
  
  

Base Trade Arrows
	The number of trade arrows a city produces from worked city squares.
Source City
	Home city of the caravan.
Destination City
	The city to which the caravan is delivered.
Distance
	The number of squares separating the source and the destination cities.
	Imagine Civ2-map turned by 45 degrees. Then you see that map is a simple grid of squares.
	Take the "rectangle" defined by the position of the unit and the position of the city (all sides of rectangle are built by squares connected by lines, not by edges).
	Distance = (length of longer side of rectangle) + 0.5 * (length of shorter side of rectangle)
Foreign Delivery
	X1	The Source City and the Destination City are both part of the same civilization.
	X2	The civilization of the Source City differs from the civilization of the Destination City.

Multiply the results of the Basic Formula by all the multipliers listed below rounding the final result up, if necessary

Commodity Demand Multiplier
	X1	any commodity not demanded
	X2	Hides, Wool, Beads, Salt, Copper, or Dye
	X2½	Cloth, Coal, Wine, Silver
	X3	Silk, Spice, Gems, Gold
	X3½	Oil
	X4	Uranium
Roadway Multiplier
	X1	source and destination cities are not connected or are connected but not by the most direct route
	X1½	connected by road
	X2	connected by rail
Halving Factor
	X1	source civilization has discovered Navigation or Invention or the game turn exceeds 200
	X2	none of these conditions met
Railroad Multiplier
	X1	if Railroad has not been discovered
	X2/3	if Railroad has been discovered
Flight Multiplier
	X1	if Flight has not been discovered
	X2/3	if Flight has been discovered
Superhighway Multiplier
	X1	neither city has Superhighways
	X1½	one city has Superhighways
	X2	both cities have Superhighways
Freight Multiplier
	X1	if the trade unit was not Freight
	X1½	if the trade unit was Freight
Continental Multiplier
	X1	source and destination cities are on the same continent
	X2	source and destination cities are on different continents
Airport Multiplier
	X1	neither city has an Airport
	X1	one city has an Airport
	X1½	cities are on the same continent and both have Airports
	X2	cities are on the different continents and both have Airports

Robert Lancaster upon who's ground breaking research this paper is based.
Winkler who's ancient scrolls made Lancaster's formula common knowledge.
Quantum Satis for his reseach and the pathways image.
All the contributors on the Apolyton Strategy Forum, especially; Caesar the Great, DaveV, samson, Gastrifitis, arii, Scouse Gits, SlowThinker, La Fayette. Their discussions and discoveries have embodied and broadened the understanding of trade in civ2.