Re: Totally OT - Highway Question - Is 100 Metres Enough

And so would my morris 1100. Under perfect conditions. As probably were your tests. "Accidents" occur when some conditions (which includes driver attitude) are less than perfect. Allowances must be made for such conditions. Most drivers are incapable of making perfect decisions at all times, they may be tired, have had a row, it may be raining etc....

A safety margin is essential. 100% doesn't seem excessive.

stopping distance (ft) = v(1+v/20) where v is the speed in mph

or v + v^2/20 thinking time approx 2/3 second and 0.6G ?

Then why was it not included in the original figures for the vehicles current at the time then? ;-)

Its probably more to do with the requirements of the MOT which only require

The message from Tony Bryer contains these words:

Perhaps it was the braking test I was thinking of, not thinking distance. :-)

I have now found 2 of my Highway Codes and the earlier one copyright

So 40mph on a not particulary busy motorway is OK then?

Many modern cars can pull over 0.6g in a corner, they can usually stop much better than that.

Most bods who tried found they could stop in the dry within 55m including thinking time. If you accept the highway code thinking distance at 70mph (31m/sec) being 21m, then that only leaves 32m to actually stop in.

In g terms that gives us:

v^2 = u^2 - 2as

a = (v^2 - u^2) / -2s

a = (0 - 31^2) / -64

(It maybe that their thinking time in these tests was less than in real life because they were anticipating the event).

Its more than the legal minimum and large vehicles on motorways do less than that at times.

I take it you don't see them when you drive on the motorways.. asleep maybe?

Indeed.

However to exactly keep within a speed limit means spending most of your time on cruise control or looking at the speedo all the time. Hardly conducive to safety.

Does.

You pull out in front of another car, driving very slowly, and watch what happens..

You try dreiving non stop to teh other end of teh country at 20mph, and see hwo tired you get, and how many accidents you cause.

No, its the trees leaping out in front of you, stupid.

The message from John Rumm contains these words:

The handbooks for the 60s/70s Lotus Elan and Plus 2 contain the following:

"capable of exceeding .9g retardation" and "capable of exceeding .8g lateral side load".

Were they really 40 years in advance of their time? :-)

My money is on them ignoring thinking time completely.

Ive got no problem with anyone doing that If its uncrowded. Ive done 25mph down the M1 towing about 2 tons up a steep hill.

I have to say that the tailbacks it caused were embarrassing and frightening.

Although not illegal it was in my opinion dangerous.

An accident is caused by tow objects at different velocities occupying te same space. Whether one is too fast, or the other too slow, or both in the wrong place, is open to endless argument.

However the fact remains that if you insist of travelling at a vastly different rate from those around you, you are a de facto hazard to them.

If you decide to drive down a mortorway at 40mph, the only safe thing is for everyone else to drop to that speed. You MAY consider that is precisely what should happen, but the days when everyone else magically conformed to YOUR opinion were left behind the moment your mother whipped her tit out of your mouth.

Which is permanently switched off because they think they are driving slowly..

I have never had an accident when exceeding a speed limit..

IF you are a habitual fast driver thinking distance is about 0.2 seconds or less.

However 0.6g is pretty fair..many trucks and vans won't do that..many sports cars will do .8-1g or so..but few more than that.

In the days when I first saw that,a Morris 1100 was a pretty modern car. Now my cousins sit up and beg ford popular with cable brakes on oversized crossply motorcyle tyres..was a different thing altogether.

Even then they had to write rules for idiots in crap cars. But in those days they weren't enforced for intelligent people in decent cars, by Big Brother cameras.

Yep. At least with a horse you can blame someone. Deer you can't.

that are largely unenforced.

What legal minimum, references please?

I've yet to see any signage that there is a minimum limit on entering a motorway or the end of a minimum limit when leaving. Indeed minimum speed limits are very rare in the UK.

Not very often, these days most wagons sit at 56mph on the limiter no matter the gradient. Other large vehicles, mobile cranes etc, have flashing orange beacons and/or an escort.

No, at least not wagons or large vehicles without beacons. The dangerous ones are ordinary cars doing 40mph.

Luck. Do I take it that you have had an accident while driving below a speed limit?