[galdosdi]

That's true, but depending on the local driving culture, this may just lead to many vehicles cutting in front of you and making the gap vanish. In metro NY/NJ, at stop-and-go speeds on freeways, 1 to 2 car lengths seems to be about as much as you can safely leave without it quickly being snatched away. Too bad.

[bashinator]

Cars cutting you does not make the gap vanish - you just have to slow down marginally more for a short amount of time.