[Alupis]

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.

[galdosdi]

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.