No sweat: Why light rail doesn’t buckle in cities far hotter than Portland

Cooling technology keeps systems in other cities from breaking down during hot weather.

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The heat wave is tough on Portlanders who tend to prefer a more temperate climate. But as the following tweets indicate, the bout of extreme weather is proving even tougher on TriMet:

Computer problems were so severe this morning TriMet had to stop checking fares. The agency’s woes raise the question: How do cities in much hotter parts of the country manage their transit systems?

It’s always hot in Arizona, but temperatures were so high this summer — topping 120 degrees — that flights were cancelled and street signs melted.

Meanwhile, the city’s light rail system kept chugging along, says Susan Tierney, communications manager for Phoenix’s Valley Metro.

Tierney says the rails can withstand extreme heat and are specifically designed to operate when temperatures exceed 110 degrees.

Valley Metro is one of the only systems nationwide that can function in such high temperatures. Its hardiness is anchored in a cooling management technique. Trains rely on air conditioning to cool the power facilities, signal houses and fare vending machines.

One of TriMet’s biggest problems during hot weather occurs when overhead wires expand and sag toward the ground. Reducing train speed helps prevent damage to the system as trains pass under the wires.

Tierney says Phoenix mechanics calibrate the wires, and that “rail tracks can expand in extreme heat because the system is built within the existing streetscape.”

The city of San Diego doesn’t get nearly as hot as Phoenix. Nevertheless, the Metropolitan Transit System fares well in high temperatures, according to Rob Schupp, MTS director of communications. 

“If there are slow orders, it is usually due to the electrical provider (San Diego Gas & Electric) having rolling brown outs which impacts the delivery of low-voltage power to switches,” Schupp says. “In extreme heat, there is increased danger in the rails expanding and popping joints apart, but we have not experienced that.”

In Houston, heat has never posed a problem for the Metropolitan Transit Authority, even as temperatures rise above 100 degrees, spokesperson Lauren Whitley says.

There are no plans for weather-related complications because the system has yet to experience any, says Whitley.