In past posts, we looked at the pavement aging curve and the role it plays in how much it costs to move, or even just hold, a city's average PCI. The natural assumption, and the one we started with, is that the relationship is continuous: the lower your PCI, the more it costs to maintain, scaling up steadily as you climb. We ran the actual numbers on four real city networks to test that assumption. It turned out to be wrong, in a way that's more useful than the original assumption would have been.