What if we move [Path New] over to Detail, and then bring SUM([Flow]) onto Color? Not sure if this is exactly what you're going for but it allows us to color the lines based on the Flow values. We can also play around with using a continuous field and discrete field to change how the color gets applied. Hopefully this can at least get us pointed in the right direction
Let me know how it looks.
Travel Path Example_new.twbx 82.9 KB
Thanks for the quick response. When I do that the arcs disappear, and we're left with just circles over each zip code. That's been a common occurrence as I play around with this problem.