It’s a cruel irony that you can get a free ride to a cooling center on TriMet’s MAX light rail, but you might suffer heat exhaustion waiting for the train to get there.

If there’s one truism when it comes to Portland transportation, it’s that when temperatures go up, the speed of light rail goes down. That’s not ideal, because not only do many folks rely on the MAX system, it’s another way public transit fails in the mode choice competition with cars.

Today is hopefully the last day of extreme heat, at least until the next wave hits us. And as per tradition, TriMet has told MAX riders to expect delays of up to 15-30 minutes due to the heat. Why does this keep happening?

It has to do with the overhead wires that provide electricity to power the trains. Known as catenary wires, these wires must maintain tension in order for train operators to travel at normal speeds. When overheated, the contact wire expands and starts to sag. If an operator goes too fast, the catenary wire could lose contact with the train’s pantograph (a tensioned arm on the roof of the train that connects to the wire) and stall out completely. The slower train speeds and/or temporary stoppages have a ripple effect across the entire system, and delays are inevitable.

Also inevitable are angry customers who just want to get out of the heat. A few days ago after a Timbers game, riders experienced delays of more than 30 minutes. Stories like this lead to frustration and further erode the public’s confidence in public transit at a time when the system desperately needs to win back riders.

Put another way, when catenary wires lose tension, Portlanders gain it.

To counter the increasingly common phenomenon of extreme heat and its impact to their light rail network, TriMet uses a system of weights attached to the poles that hold catenary wires (see video above). As temperature rises, the weights (which weigh about one ton) sag to tension the wires. The weights can rise or fall as much as one inch per degree of temperature change. Sometimes it’s so hot the weights come to rest on the ground and TriMet has no choice but to tell operators to slow way down in order to maintain consistent connection between the pantograph arm and the wire.

With 100 degree-plus temps forecasted today, delays will likely hit the system once again.

So what’s a transit agency to do about the all-powerful sun whose heat is becoming an ever larger force in our daily lives? One problem in Portland is that our light rail system wasn’t built with frequent extreme heat events in mind. In a statement issued last month, TriMet said their MAX system, “was originally designed to operate in the climate Portland enjoyed in the 20^th century.” And despite investments they’ve made for heat resiliency since 2018, temperatures above 100 degrees can still cripple their system.

Mitch Green is an energy economist and candidate for City Council District 4. Before this current heat wave, he shared messages on social media that Portland needs to re-invest in its basic infrastructure to handle extreme weather events, lest we remain, “in a state of precariousness.”

Green replied to TriMet’s latest announcement about MAX delays on X yesterday by saying, “We’ve got a situation where the structures and systems we have today, as a product of past investment, are no longer calibrated to the urgency of the moment. But, we don’t throw up our hands: we invest again.” Green says MAX delays aren’t TriMet’s fault and that settling into finger-pointing and status quo investment levels will never allow us to build the “truly resilient systems” we need.

So next time you’re mad about a MAX delay, after pointing your finger at TriMet, point it at the sun — and then point it at yourself. We’re all in this together and it will take a collective effort to fix these problems.

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— Before heading out, check TriMet system alerts here.