We have something like that in eu with road markings. Both for clear weather and fog/rain. They mark some of the lines differently, and tell you how many lines you should have between you and the car in front. I think they were first trialed and then printed in several places.

Cool. But I'm thinking this box floats in front of your car on the road in real time. See you're driving and ahead of you on the road is this box. At night it might interfere with your night vision, might have to workshop that a bit.

There's a couple of bits of motorway in England with that, I'm pretty sure the M6 and the M1. There are white chevrons painted on the road and you keep two of them between you and the car in front.

Also "Keep Two Chevrons Apart" is going to be the name of my specialist Citroën breaker's yard.