"Taking A Train During A Heat Wave? Watch Out For ‘Sun Kinks’"

"As tracks heat up, they expand and buckle. That's forcing rail operators to adapt as the climate warms."

"One of the iconic sensory experiences of riding a train is actually the sound of ingenuity. As steel railroad tracks heat up, they grow: 1,800 feet of rail expands by more than an inch for every 10 degrees Fahrenheit of temperature increase. So rails used to be laid down in sections — each between 30 and 60 feet long — with small gaps.

“The very specific railway noise that you hear — chuchat … chuchat … chuchat … chuchat … chuchat — is because there is a gap between the rails, and this gap is meant for such expansion,” said Dev Niyogi, who studies urban climate extremes at the University of Texas at Austin.

Still, in a severe heat wave, the rail can swell until the underlying ties can no longer contain it. Then the rail gets visibly wavy, morphing into what’s known as a sun kink. That’s a serious hazard for trains, which can derail on misaligned tracks. In extreme cases, the track can violently buckle, going from a straight shot to grotesque curves almost instantly. So if it’s excessively hot out, rail services will slow their trains as a precaution, which provides less of the mechanical energy that can lead to buckling. Amtrak, for instance, restricts speeds to 80 miles per hour if the rail temperature hits 140 degrees. That was partly the reason behind Amtrak delays in the Northeast Corridor, which runs between Washington D.C. and Boston, during a brutal heat wave last month. (Amtrak did not respond to multiple requests to comment for this story.)

As extreme heat waves get worse, more tracks will turn into sun kinks — disrupting commuter rail service that reduces carbon emissions and slows that warming. In 2019, a study estimated that the U.S. rail network could see additional delay costs totaling between $25 billion and $45 billion by the year 2100, in a scenario that assumed greenhouse gas emissions decline in the next 20 years."

Matt Simon reports for Grist July 9, 2024.


Source: Grist, 07/10/2024