Mike Bristow wrote:
In article ,
Tom Anderson wrote:
No, that's irrelevant - HC rule 105 sayeth that "the safe rule is
never to get closer than the overall stopping distance"; that
applies to cars that are cruising at constant speed, in which case
my calculations are correct. The stuff about average speed during
braking is captured in the calculation of that overall stopping
distance.

If we're to play with real-world numbers, throwing the HC out the
window would be the best bet. I think that a gap of 2 seconds
between vehicleS is reasonable (ie, 30 cars per minute per lane).

The HC in my view is quite reasonable about this. It says (not in
exactly these words):

Make sure you leave enough room to avoid hitting the bloke in front if
he suddenly slows down or stops. If you want to be sure to be safe,
never get closer than the overall stopping distance, but in practice a
gap of 2 seconds is OK (but leave more time if wet/icy or driving
something that doesn't brake too well).

Saying "the safe rule" is the HC's way of hinting that good real-world
drivers might not always slavishly follow it.
--
Richard J.
(to e-mail me, swap uk and yon in address)