'Heat kink' could delay light rail on hot days in King County

Hot temperatures around Seattle this month could mean potential delays to light rail service.

Sound Transit has extra work to do during these summer months: watch the tracks closely.

“As rails get hotter, what you see, especially on mainline class one tracks, is concerns about thermal expansion, which is the new term for heat kink,” Henry Bendon, a spokesperson for the transit agency, told KUOW.

As metal tracks warm up, they can expand, warp, and even buckle.

When daytime highs get into the 80s or 90s, Sound Transit crews inspect the tracks, looking for any expanding metal that could slow down service.

"At really, really high temperatures, you could see a situation where we might have to slow down trains just to continue operating them,” Bendon said. “We take that section of track out of service, and we would single track around it."

This has happened in hotter places like Austin. Some Amtrak trains have to slow down on the East Coast during summer when tracks get really hot.

Thankfully, with temperatures in Seattle only reaching the 90s, that’s not common here.

“Not to brag,” Bendon said, “but we have really nice track. It's new, it's well maintained. We have excellent teams that are out there working on it all the time.”

So far, this summer in Seattle hasn't gotten hot enough to cause concern.

The National Weather Service in Seattle says to expect temperatures to reach the mid to high 80s this weekend and next week.

Last month, the 2 line on the eastside was disrupted when an overhead wire sagged in the heat.

Bendon said inspectors and train operators will be watching the roughly 40 miles of track in the sun this week and next.