[netsp]

The point of counting seconds instead of distance is that it works at any speed. People tend to keep the longest (time) distance at suburban speeds.

7 seconds at highway speeds can be over 200 meters.

I'm all for safety, but that is excessive.

[Retric]

If you break faster than most other cars will often get rear ended, it's not just cushion for you but also the car behind you. Try to break from 70 on an empty road after 2 second reaction time and see how long it takes and how far your car travels, and then consider what would happen if someone was tailgating you at the time.

PS: Thinking you have a 2+ second reaction time helps to cover when you are not directly looking at the car ahead of you. The less of that cushion you have the more you need to focus on the car in front of you.