A thing that has puzzled me before and puzzled me again this week:
I, although living in the US, am not going to burst may brain by calculating this in miles and feet.

here we go

On the freeway I drive 25 meters behind a car of another make, which is clearly running on cruise control. I set my cruise control. We drive at 100 km/h. 10 km later the distance to the car in front seems the same. If we say it has (without me noting it) changed 1 m the variation is still less than 1/10.000.

1) when seeting the cruise control I am sure I am not driving at a speed within 1/30.000 km/h of the car in front of me, that precision would be impossible.
2) the cruise control, I am sure, is not that precise
3) it works the same at various distances so 'drag' is not it.
4) there is uphill and downhill.

How does that work so well in this situation?
Have you the same experience.

Erik