Cops who tailgate you...

[TJeno]

here safe following distance is 1 car length for every 10 mph, so 70 mph, 70 feet. iirc you travel 360 feet a second at 55 mph ( a foot ball field a second) you have a minimum of a 1 second to react, you do the math, one car length is not far enough away, and if you drive a big truck you stay even further back, and i get cut off all day for it. i take crap all day i tell ya lol.

granted most do 1 length car at any speed.

I usually just use the 2-second rule, that's how I determine if I'm too close or not. At any given time, say doing 60 down a highway, I select a given point (say, a no-passing zone sign) and count two seconds out in my head. If I reach that same point before the 2 seconds is up, I know I'm too close. I'm pretty sure that's also what's recommended by the DoT, at least in the state of Iowa.