https://www.cnet.com/roadshow/news/traffic-talk-ford-vanderbilt-2018/

Vanderbilt University and Ford are working on finding a solution to these phantom traffic jams, and surprisingly, their fix involves using something that's already fairly common on modern vehicles: adaptive cruise control.

You see, a phantom jam (excellent band name, right?) starts when one or more drivers at the head of a pack of cars applies the brakes. Seeing the brake lights, the people behind them naturally slow down, and while it might be a relatively simple thing to speed back up, there is already a ripple effect being sent down the road from brake light to eyeball, and the time it takes to brake, reaccelerate and then re-establish a safe following distance continues to grow.