> At least 2-3 seconds, minimum. Did you not take any driver's ed classes?
GP is right, though, it is highly context dependent. If you are following another car and paying attention, then two seconds is enough if they slam on the brakes. There is an implicit assumption that two cars have roughly equivalent braking ability.
But what if they do some sort of assisted stop? Bridge abutment. Head-on collision. Or what if there is a stopped car in front of the car in front of you, and the car in front of you swerves out of the way leaving you bearing down on an unexpectedly stopped car in the lane? 3 seconds won't be enough.
I still remember vividly many years ago coming around a high speed sweeping corner behind another car, at a perfectly reasonable stopping distance, and then they jerked the wheel into the oncoming lane and suddenly I was facing the back of a stopped car. That was exciting. I did not hit the car, but it was close, very close. The only way to avoid that is a stopping distance much greater than 2-3 seconds.
GP is right, though, it is highly context dependent. If you are following another car and paying attention, then two seconds is enough if they slam on the brakes. There is an implicit assumption that two cars have roughly equivalent braking ability.
But what if they do some sort of assisted stop? Bridge abutment. Head-on collision. Or what if there is a stopped car in front of the car in front of you, and the car in front of you swerves out of the way leaving you bearing down on an unexpectedly stopped car in the lane? 3 seconds won't be enough.
I still remember vividly many years ago coming around a high speed sweeping corner behind another car, at a perfectly reasonable stopping distance, and then they jerked the wheel into the oncoming lane and suddenly I was facing the back of a stopped car. That was exciting. I did not hit the car, but it was close, very close. The only way to avoid that is a stopping distance much greater than 2-3 seconds.