Why one highway exploded this summer — and why many more are at risk

It was another sizzling summer day in late July, with temperatures nearing 100 degrees, when one of the main roads cutting through Greenville, Texas, finally just gave up.

The stretch of U.S. Highway 69 kept expanding in the extreme heat until it exploded, creating a sharp, two-foot-tall ramp where it broke at the pavement joint. Most of the traffic in this Dallas exurb drove around it.