What is the definition of a "car length"

Here is one answer obtained via Google. I don't think there is an "official" definition:

WikiAnswers - What is the average length of a car

 

The two second rule is much easier to follow, even if you knew how much a car length was. It works at any speed, except in urban traffic where it's almost safer to tailgate than be cut off.

 

i'm in for 20'

 

Very few private passenger cars were ever 20 feet long. The average back in the olden daze when the 1 car length per 10mph rule was drivers ed wisdom was about 15 feet. That is essentially 1 second which isn't enough unless you are really on top of your game. 2 seconds is the closest you should follow if traffic allows it. If you are following at 2 seconds and people keep cutting in front of you, then you might consider one second.

3 seconds is better but not realistic except on the open road.

 

@xs650

+1

That was what I had figured out too ... the old 1 car length per 10 mph rule is roughly the equivalent of the 1 second rule.