https://techcrunch.com/2018/07/28/tapping-into-the-power-grid-could-predict-the-morning-traffic/

Why is there traffic? This eternal question haunts civic planners, fluid dynamics professors, and car manufacturers alike. But just counting the cars on the road won’t give you a sufficient answer: you need to look at the data behind the data. In this case, CMU researchers show that electricity usage may be key to understanding movement around the city.

The idea that traffic and electricity use might be related makes sense: when you turn the lights and stereo on and off indicates when you’re home to stay, when you’re sleeping, when you’re likely to leave for work or return, and so on.