On Tue, 2 Aug 2005, Tony Bryer wrote:

In article , Tom
Anderson wrote:

Then they're travelling too close together. Unless the traffic's
flowing at 40 mph, at which speed 2 seconds is almost enough.

Your arithmetic is wrong in that during the period you are stopping your
average speed is only going to be about half the initial speed, so you
would need to double your calculated times.

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.

What you ignore, and what lies behind the 2 second rule on faster roads
with good visibility is that the car in front is not going to stop dead
- unless something really catastrophic happens.

True, but whoever wrote the HC didn't seem to think that mattered - rule
105 commands you to "drive at a speed that will allow you to stop well
within the distance you can see to be clear". Perhaps they had those
really catastrophic somethings in mind?

tom

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