I wouldn't say recently... it's a symptom of how the roads and highways were built in the US. They are essentially in a constant state of construction due to repaving needs, growing traffic congestion, etc.

What sort of "source" do you expect would exist for this? It's just the day-to-day job of DOT.

I guess I misunderstood your usage of "have become" to mean that this is a new state of affairs, and it didn't use to be this way in the past.

In the midwest, we have two season, Winter, and road construction. As soon as winter ends, road construction begins. Neverending road construction.