Scorching heat waves across the central United States have taken a toll on area roadways this month, forcing state agencies to issue advisories for motorists to drive with extra caution.
Reports of buckling roads have come in from Iowa, Minnesota, Nebraska, South Dakota, Colorado, Missouri and Wisconsin as temperatures have soared to dangerously high levels.
The Minnesota Department of Transportation (MnDOT) issued a press release on June 10 cautioning residents to "expect the unexpected" after hot weather caused several "blow-ups" of concrete pavement along Interstate 90.
The primary factor behind this often unexpected danger is thermal expansion which causes the roadways to buckle or shatter, according to the Nebraska Department of Roads (NDOR).
"A pavement blow-up occurs when the roadway surface expands at a crack or joint where moisture has seeped in," NDOR states. "That crack weakens the pavement and the heat causes the pavement to buckle and warp. This usually occurs on very hot afternoons, as the maximum temperature for the day is reached, typically during afternoons with 90-degree or hotter temperatures."
At least a dozen pavement blow-ups have been reported in Nebraska's District 1, located in the southeastern part of the state.
In South Dakota, the state's highway patrol posted images that showed part of the interstate jutting out of the ground forming what looked like an unwanted ramp.
In Sioux Falls, South Dakota, blow-ups requiring immediate repairs have occurred in 15 different locations in the past two weeks, according to Travis Dressen, Sioux Falls area engineer for the South Dakota Department of Transportation.
Dressen said the number of buckled roads that maintenance crews have responded to in June is already about double the total number from last summer. However, he noted that this repair work doesn't impact already scheduled roadway reconstruction.
Certain roads may fare better than others in terms of withstanding the heat, and that is due to the type of pavement that was used in construction.
"Blacktop (bituminous) pavement is a more flexible material and does not usually blow up but may create a bump similar to a frost heave, especially in areas where concrete and blacktop meet," MnDot said in a press release.
Typically, it's more of a problem for concrete surfaces, which are not as flexible.
We've seen reports of roads buckling around Sioux Falls today. Ever wonder why that happens? pic.twitter.com/pj6brlFSnP— NWS Sioux Falls (@NWSSiouxFalls) June 10, 2016
While there is not a specific temperature that will set off an alarm for engineers, once the humidity began to increase and temperatures reached the mid- to upper 90s F around Sioux Falls, that's when the recent problems began, Dressen said.
In addition to the sudden rise in temperature, the Sioux Falls region received a lot of rain earlier this year, so crews have noted moisture between the joints in the road.
"We know there's some subsurface moisture there, which doesn't help things," Dressen said. "With the quick rise in temperatures, [that] really starts to trigger that blow-up to occur."
Buckling is a fairly common problem early in the summer season, the Wisconsin Department of Transportation said. While it's impossible to tell when pavement may give way, the agency provided several ways to prepare.
Motorists are encouraged to slow down, buckle up and eliminate distractions while keeping an eye on slowing traffic and roadside workers. Utilizing a state's 511 travel information system can also provide the latest on incidents or delays.