PORTLAND, Ore. – During Portland’s heat wave many TriMet MAX riders sounded off about their frustrations regarding train delays.

“I thought it would be capable and more manageable and prepared but I guess not,” said one rider in Portland whose commute to Tigard typically takes an hour. This week, it took almost double that time.

Many have wondered why the trains slow down in extreme heat.

TriMet said the answer is simple. It’s because of how the light rail system was built. The tracks are made of steel and wires of copper, both of which expand in the heat. They say for that reason, trains travel slower to prevent damage and look out for hazards.

TriMet warns riders when the temperature reaches 90 degrees, they should expect delays because the trains will slow down. As it gets warmer, delays are more extensive. TriMet says to expect delays of 30-45 minutes when its 105 degrees, like it was on Thursday.

TriMet High Heat Cheat Sheet

On social media, some have pointed out how the light-rail system in Phoenix runs with no issues in similar conditions. TriMet says that’s because the city spent more money to anchor the rails in concrete. Portland’s system is built to run in its more moderate conditions.

However, TriMet did build its newer Red Line with anchored rails. They said if results positive, they’ll consider expanding.

In the meantime, the agency continues to ask for patience as temperatures are expected to be in the 90s for much of next week.