Minimizing Heat Delays on MAX

Last year, we shared a bit about why our trains slow down when it heats up — basically, temperatures above 90 degrees bring the possibility of rails expanding and kinking, or overhead wires sagging.

We know how it feels to slow down in extreme heat.
We know how it feels to slow down in extreme heat.

Before we go any further, we should answer a common question: Why didn’t we build track that can withstand higher temperatures? Surely, places like Phoenix don’t have this problem — right?

It’s true. Hotter places like Phoenix, which experience many 90+ degree days, don’t have this problem. But they do have trouble at the other end of the spectrum, when it’s cold out. This is because transit agencies build systems to work within the temperature range of their region, with the rails and overhead wire resting (neither expanded nor contracted) at the average temperature. For reference, the average temperature here is about 55 degrees, compared to 75 degrees in Phoenix.

Nobody wants a slower trip in extreme heat. You’ve got places to be, and we’re trying to stick to a schedule. That’s why we’re looking into ways to speed trains up when it’s hot out — we’ve already come across a simple solution that seems to work: track anchors. These were initially installed along the new Orange Line track for other reasons, but later we noticed that the rail here didn’t seem to affected by high temperatures.

So last spring, crews installed similar anchors to the rail ties of a segment of Red Line track that we knew to be especially prone to sun kinks. These have kept the rail in place, even on warm days (when rail temperatures can approach 20 to 30 degrees hotter than the air temperature). This simple step, which didn’t even require disrupting service, saved approximately 25 to 30 minutes of time throughout each service day, adding back over 150 hours of increased on-time performance over the course of a year.

There’s also the issue of overhead wire sagging in the heat and potentially damaging the pantograph (the arm that connects MAX to the wire) if it drops far enough. So we’re looking into ways to give the counterweights — which keep the wire taut — more room to move.

This summer has been curiously mild, but we’ll use the hot days ahead to gather more data on how these potential solutions hold up in real life. Eventually, when we’re confident that they’re worth the investment, we’ll implement these upgrades on a wider scale. And we’ll be able to keep moving, right through the heat.


Why Our Trains Slow Down When It Heats Up

Monitoring MAX On-Time Performance

MAX System Reliability Improvements

Brian Lum

Brian Lum

I'm TriMet's Web & Social Media Specialist. I'm here to help tell our story, and to share the interesting things I find along the way. When I'm not here, you'll find me out riding my bike and taking pictures.

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