General info about stopping distances and killing people via ignorance of it.
If you are 80 feet (5 cars) behind me when I was going 117 fps (80mph), I would think you were a drunk or an idiot.
You should be at LEAST 200 feet at that speed. Seriously. Just the different in stopping distances between cars makes sub 1 second following something done by fools. The stopping distance in good conditions at 70mph is 172 feet in an X. Sports cars stop in under 130 feet at 70mph with stock tires.
Somebody with good reaction time and 2 foot driving is a 1/4 second to brake lights in cars. Normal people are 1/2 second with one foot driving. Distracted is easily past 1 second. And you gave yourself 0.7 seconds? Even the TACC can't actually make up the difference between car models when using 5 cars/80mph. If a vette nails it's brakes in front of you, and the car instantly goes max brakes, that 80 feet at 80mph will be consumed by the difference in stopping distances.
In any case, following distance should always be measured in time, not distance. Obviously following distance changes with speed.
This is naturally assuming public roads. Closed course? Rubbing is racing.