Some of my Ypsilanti readership might have the same question that I did. "So, if MDOT went through and dug up and patched Huron/Hamilton/W. Cross two weeks ago, why are they going back now and milling the whole surface off those roads? What was the point of the first go-round?"

I have unearthed The Answer. The first pass was to saw out sections and patch cracks in the underlying, concrete layer of the roads. They then patched asphalt on top to provide a smooth driving surface until they got around to the second phase, which involved milling off and repaving all of the asphalt top layer. Apparently, this is the method of doing all the necessary work that involves the least disruption of traffic.

(In some locations, such as right at the intersection of Michigan and Huron, the top layer ends up as concrete as well. Concrete has a much longer lifespan than asphalt, but is orders of magnitude more expensive to build roads out of, so they use concrete for the underlayer and for the intersections expected to see the most abuse, and asphalt top-coat for the rest.)

I find this interesting. Interesting in an, "Oh, that's interesting," way, not in a, "gee, I wish I were a civil engineer," way, mind you.