Expect Delays: Why Trains Slow Down When It's Hot

Last week I took an Amtrak train south for the holiday weekend, and there was a delay. The explanation: the track was under a 'heat advisory' and the train had to travel at a slower speed. This left me wondering what happened to the tracks when it got so hot outside - and why they couldn't travel at speed. An Amtrak passenger train. Image Credit: modified from Massachusetts Office of Transportation on Flickr. Most railroad tracks are metal and when (most) metal heats, it expands. As the tempera...