"Now that we have our inputs, let’s perform the first set of calculations for the trips between Zone A and Zone B. As we discussed, the Fratar method requires us to calculate trips in both directions and then average them.
First, let's look at T {A B} trips originating in A and ending in B. We take the future production of Zone A, which is 600 times 1.2, and distribute it based on Zone B's share of 'growth-weighted' current trips. By dividing B’s weighted trips by the sum of weighted trips to B