Re: Advice about speeding ticket please

Norman Wells <norman@xxxxxxxxxxxxxxxxx> wrote:

And when the same thing happens at 40mph, the limit will drop to
30mph....................and so on.

Which, of course, proves that it's nothing to do with road safety and
all to do with revenue generation.

No it doesn't. If you have a pinch point caused by road works,

So road works which don't create a 'pinch point' don't have reduced speed
limits?

it's easy to show that you in fact get more cars through the congested point
at 40mph than at 50mph, and more through at 30mph than at 40mph, due to
the fact that cars can safely travel much closer together at lower
speeds.

But it doesn't actually work like that does it. If all vehicles have a
strictly enforced speed limit then they can do nothing to reduce gaps
between them. All they can do is travel at the limit with existing gaps or
slow down which just swaps the gap behind them for the gap in front.

It's not a linear relationship, but down to the braking distance
being proportional to the square of the velocity. So, ignoring a
standard reaction time, cars travelling at twice the speed have to be
four times the distance apart.

Wrong. Assuming we are not concerned about large blocks of concrete or
something dropping from the sky a driver can brake and slow down more or
less as quickly as the traffic in front of him. The safe following distance
is all to do with reaction time not braking distances.

If drivers follow the 2 second rule (which is independent of speed) then
the flow rate of any lane of traffic is one per 2 seconds + the time the
vehicle takes to travel its own length. That time reduces as vehicle speed
increases without limit.

The only other (and more significant) way flow rate can be increased is by
drivers sacrificing the 2 second rule, they may be more prepared to do that
at moderate speeds.
--
.

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