Understanding DiscretionaryTrips logic

[Hussein-Mahfouz]

Hi again! Another question on DiscretionaryTrips following #283

I am trying to understand the DiscretionaryTrips logic. In your example notebook, there are 4 cases. You say "Case 4 solves the first location as case 2, and then the rest as case 3". I'm not sure I understand how case 3 and 4 work.

Let's say we have the following trip chain:

(1) Home - (2) Shopping - (3) Cafe - (4) Home -> (Anchor - Discretionary - Discretionary - Anchor)

My understanding is that the chain is solved recursively: you solve for (2) shopping, and then apply the same logic to solve for (3). Is there a way to ensure that your solution satisfies time constraints?

I'm thinking of a typical chain from the National Travel Survey which would have:

Trip ID	Origin Purpose	Destination Purpose	Start time	End time	mode
1	Home	Shopping	10:00am	11:15am	bus
2	Shopping	Cafe	1:30pm	1:55pm	walk
3	Cafe	Home	3:30pm	5:00 pm	bus

For the third trip, are you trying to find a cafe that is approximately 90 minutes by bus from home? Or does the function give more accurate destinations for the first discretionary trip?