CHARLOTTE, NC (WBTV) - Thousands of miles of train tracks cross the Carolinas, and in extreme temperatures those tracks can come under assault by mother nature.
The heat may be to blame for a train derailment in Waxhaw, North Carolina on Thursday. A freight train hauling grain and other goods jumped the tracks and spilled some of its load. Fortunately no one was hurt, but the crash cut off one of the main roads in and out of the Union County town. Luckily, the train wasn't hauling anything hazardous.
For many, it's hard to imagine the extreme heat could cause something like this. But it can happen when we have triple-digit temperatures like the east coast has experienced this week. What happens to the tracks is known as "sun kink." It's when the track buckles and becomes warped. If a train goes through the area too fast, it can cause a derailment.
Researchers have tried for decades to figure out how to keep it from happening, but no technology exists to stop it.
"The rail as it heats needs room to expand," said Larry Neal, a certified brake man who showed us how tracks can become buckled. "You see, there's four bolts that hold them in place."
Before 1950, he says rail came in 39-foot sections, and there was room left where the track comes together to give the steel room to expand in extreme heat. These days, to make for a smoother ride and less maintenance, track comes in quarter-mile strips and is welded together without the expansion joints.
On an extremely hot day, the steel expands. "The rail heats up," described Neal. "It gets to a point where the ties and everything can no longer hold it and the rail has nowhere else to go lineally so it'll pop out to the sides."
And with hot weather we've had recently, it's happening more frequently. Problems with "sun kinks," also known as "heat kinks" have turned up in Greater Boston's public transportation system. It's also happened in Philadelphia, Baltimore and on Washington, DC's Metro system. All of them are cities who've been hit in the record heat wave.
In one of the most dramatic scenes, in July 2002, an Amtrak train derailed outside Washington, injuring more than 100 people. The derailment was linked in part to sun kink.
"In hot weather, we increase our inspections of lines that could be affected," says Norfolk Southern spokesman Robin Chapman.
He said they if they do find a problem track, a so-called "heat order" goes out notifying train crews to go slowly in that area until the track can be fixed or until it goes back in place on its own when the temperature drops.
"There were a lot more occurrences of this in year's past," says Neal. "But because of better technology, better understanding of metallurgy of rail, they're improving the sun kink occurrences."
To prevent buckling railroads, often heat existing track in an effort to condition it to high temperatures. Tracks in the South are typically treated to withstand up to 100 degrees, wWhile a 90-degree temperature is used in North.
It can happen anywhere along the line. Often the problem is caught before a train passes through, but if the track bends too much we can see derailments.
The number of accidents resulting from buckled tracks have gone down over the years, from 174 in 1980 to about 40 in 2001. But so far, nothing can prevent it from happening.