When people behind don't respect the safety distance (and, for me, 1s is my level of tolerance), I switch on my warning lights. I keep them on for 20km if necessary. I know it's illegal, but if that's what it takes to make others respect my safety distance, I think it's worth it. And it's better than other (bad) solutions like hitting the brakes to test the guy's safety distance...

We should just be allowed to carry police-verified dash cams which issues fines in live ;)