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Extreme heat disrupting mass transit operations

August 18, 2023

Extreme heat is increasingly threatening public transit systems, which are considered a highly-effective way to reduce carbon emissions and progress toward clean transportation goals. To mitigate the risks to riders and infrastructure, speed restrictions and even service suspension are being issue on some of the hottest days.

Civil engineers and mass transit authorities warn that railroads or tracks could bend or buckle under the extreme heat. On August 4, in Austin, Texas, a Capital Metro operating engineer identified  a “sun kink,” or warped train tracks on the Red Line — posing a risk of derailment. The engineer was permitted to slow down the passenger train to less than 10 miles per hour and cautiously proceed over the tracks, under standard operating procedure.

Then transportation services were interrupted to avoid other trains from driving over the kink. Passengers on the same route were later bussed between CapMetro stations, so the rail contractor could repair bent rails.

Extreme weather may lead to more transit service disruptions as agencies, from coast to coast, avert damages and make repairs.

In June, 2022 the San Francisco Bay Area Rapid Transit (BART) cited — for the first time — extreme heat “causing a curve in the rail” as “the main role in the partial train derailment.” As ambient air temperature reached a high of 102˚ F (39˚ C), the rail tracks likely reached 140˚ F (60˚ C) — 25 degrees hotter than what the mass transit authority considers safe.

In June, 2021 extreme heat melted cables that power Portland, Oregon’s TriMet light rail system. The U.S. National Weather Service (NWS) reported an ambient air temperature of 112˚ F (44˚ C). All train services were suspended for two days since the “system is designed to operate in up to 110˚ F (43˚ C) heat.”

In the U.K. as national heat records have been shattered, Network Rail has painted railways white in some areas in an effort to deflect the heat and prevent warping. In Vauxhall, London, unpainted tracks warped as the they reached a temperature of 118˚ F (48˚ C). In direct sunshine, railways can become as much as 20 degrees hotter than the ambient air temperature.

Nationwide, passengers have been advised to avoid all unessential travel and train services have been cut.