What's a sun kink? How extreme heat hits Austin railroads

AUSTIN (KXAN) -- As Austin continues its longest consecutive stretch of triple-digit days in recorded history, it's not just residents who are feeling the heat -- the city's local railroads are, too.

When temperatures around the globe peak, rail operations have to adjust services to battle the heat's impacts, CapMetro said in a blog post Thursday. For Austin's transit authority, that means trains must slow down on tracks once the railroads reach 135 degrees or warmer.

Along CapMetro's 32-mile Red Line running from downtown Austin to Leander, slower speeds have led to schedule modifications, per the transit agency. The same practice was implemented for the Red Line last summer.

“There’s just no way around it,”  said Andy Skabowski, CapMetro's executive vice president and chief operating officer, in the blog. “You have to slow down the trains when it’s hot like this in order to avoid putting too much stress on the tracks. This type of heat can cause sun kinks – and that’s exactly what happened a couple of weeks ago.”

What's a sun kink and how is it caused?

So what, exactly, is a sun kink? The phenomenon is the result of extreme heat bending, warping or distorting rail tracks. It's an issue CapMetro officials encountered on Aug. 5, when a train engineer discovered a buckled track between the Highland and MLK Jr. stations.

“When that happens, we have no choice but to stop using that part of the track and we call for a bus bridge immediately,” Skabowski said in the blog. “You can’t run a train over warped tracks. It can cause all types of safety issues – one of them being derailment. Thankfully, this happened on a Saturday and we were able to get this fixed in time for Monday morning service.”  

CapMetro isn't alone in its reduced-speed rail efforts to combat the heat. The Washington Metropolitan Area Transit Authority in Washington, D.C. announced it would also slow down its trains because of record-breaking temperatures. Texas' scorching temperatures have also led to service impacts on the Dallas Area Rapid Transit rail operations.

CapMetro officials said in the blog that service alerts will be issued for passengers when trains are running more than five minutes behind schedule. Riders can sign up for CapMetro alerts, check out the CapMetro mobile app or monitor status updates posted at each rail station.