Euro NCAP actually mandates that a following distance should be part of adaptive cruise control. A lot of manufacturers have turned this into a distance meter on the dash, in addition to the automatic braking. When I test-drove a Renault 5. I could see a little bar graph measuring how close I was to what the car thought was safe. Which turned out to be a lot closer than I would be comfortable driving! That is, the car would have allowed me to get much closer before it would have activated any automatic braking.

(the irony of looking at a meter on the dash to duplicate a piece of information I should be very clearly seeing out of the windscreen was not lost on me, though)