Is the massive heat wave slowing down public transit?

If you live in one of the 26 states that are currently under a heat advisory, you’re not imagining it if your daily commute feels slower than usual. Heat waves don’t only make people sluggish — they also slow down public transit.

Trains must operate at slower speeds in oppressive heat like the 90- to 100-degree temperatures currently baking much of the Northeast and Midwest. According to Masoud Ghandehari, a professor of urban systems engineering at New York University, this is because high heat causes the mechanical infrastructure for trains to expand, particularly components that are above ground and in the sun. And electrical systems like switches are prone to more frequent failures.

This means the trains have to slow down to try to avoid the increased risk of a mechanical problem or failure. Trains across Chicago, Boston, New York City, New Haven and Washington, D.C., have been experiencing delays “due to temperature-related speed restrictions.” The high temperatures are expected to continue through Wednesday, and affected residents have been encouraged to take precautions to stay cool.