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Posted to uk.d-i-y
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Totally OT - Highway Question - Is 100 Metres Enough
wrote:
On 12 May,
John Rumm wrote:
The highway code shows a minimum car to car distance of 2 seconds, which
at 70mph equates to 62m at or just over 200 feet. At 100mph that equates
to 88m.
You know you really ought to have a look at the book if you are going to
quote it, rather than just making up stuff.
Modelling the system mathematically putting in reasonable G figures, the two
second rule breaks down at about 60 mph, and is nearer 3 seconds at 70mph,
equating to 300 feet. doing the sums for 100mph would be somewhere near
double the distance. Unless you want to end up in the boot (or worse) of the
vehicle in front.
This doesn't take into account the almost doubling of kinetic energy
available for destruction at 100mph as against 70mph.
The 2 second rule is a reasonably accurate rule of thumb, over the speed
range it is intended for. If everyone would stick to it at 70mph, things
would be a lot better than they are at the moment on our roads.
The rule is not intended to prevent collisions with stationary objects
or we would all be dead. It is there as a decent enough time to assess
the behaviour of the car in front and get the brakes on as fast as he
has them on.
If there IS a pile up ahead, and cars have come to a halt, it's totally
inadequate anyway..
The best you can hope for is that you are not just slavishly following
some rule, but can see issues up to a couple of miles ahead. One reason
I don't like being the meat in a 56mph trick sandwich. No visibility,
even if you drop way back.
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