What do you mean? Distance is a function of time and speed, and on any adaptive cruise control is factored with multipliers based on the minimum reaction time, which is exactly a second.
Interestingly, when abandoning the radar for Vision we lost factor 1, guess why...
So it doesn't really matter if you graphically "see" a distance displayed on the car, what it is really calculating is a multiple of the distance driven before the driver realizes the danger and hit the brakes, starting with 2 seconds (which we also use in aviation as a minimum reaction time for aborted takeoffs, conservatively). Which ironically is the minimum time wasted nowadays reading a message on the phone.
A good rule of thumb in kmh is taking the tenths of the speed and multiply them by 3 to find the meters wasted. In mph you get feet by multiplying mph per 1.5. That's the minimum distance travelled in a second, even before hitting the brakes. E.g. at 55 mph you already travelled approx 80ft in a second, double in two.
