How do stoplights know when to change?

Waiting for a stoplight to turn green can be really annoying, especially when you’re running late. It would be awesome if you had a magic wand you could wave to get the light to change. But alas, such things don’t exist. But how do stoplights know when to switch colors? We asked Jerry Kotzenmacher with the Minnesota Department of Transportation to help us find the answer. Got a nagging question that just won’t yield? Send it to us at BrainsOn.org/contact, and we’ll put you in the express lane to answersville.

You can listen to How do stoplights know when to change? online on Radio and Podcast. Open the player on this page to stream the available audio.

How do stoplights know when to change? is an episode from Moment of Um by Lemonada Media.

This episode is 6:09 long.

This episode was published on Jun 4, 2025.

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