Re: Victory for green lanes

The message <68fp0hF2t66qvU1@xxxxxxxxxxxxxxxxxx>
from Peter Clinch <p.j.clinch@xxxxxxxxxxxx> contains these words:

I have just had a quick trawl on the web. Prior to that all I could have
told you about foreign limits was that Germany still doesn't have a
maximum speed limit on much of its autobahn network and the Isle of Man
has so far resisted every attempt to give it a maximum speed limit.

The situation these days is complicated by the speed limits introduced
as fuel saving measures but prior to the first oil crisis I suspect that
the UK was in a minority of nations in having a national limit. As it is
a good many countries have motorway limits in excess of the UK limit.

And a good many don't: see
http://en.wikipedia.org/wiki/Speed_limits#Speed_limits_in_specific_countries
Reading further on I see you've got to that page, but conveniently swpet
aside the fact that international motorway limits are all in a pretty
close ball-park.

I see you conveniently swept aside my comment above "speed limits
introduced as fuel saving measures". Incidentally the national speed
limit on single carriageway roads is a remnant of the fuel crisis
limits.

And why would civil servants, who only a few years earlier, had helped
Marples frame the motorway legislation in such a way as to make it
expensive to give motorways speed limits (which is why we have the
absurdity of a posted limit on every slip road leading to a 70 mph
section of a motorway) change their spots.

Maybe folk had learned a thing or two about motorways since the original
spec? It remains patently absurd that you're trying to bin blame for
the UK's traffic ills today on Barbara Castle: traffic law in the UK is
not clearly that different to overseas countries today and she was out
of office long, long ago.

No I just blame her for the imposition of the 70 limit and the spin
needed to justify it.

But cyclists were much more frequent way back when and there is no way
you can make the argument that rare cyclists are more at risk than
frequent ones stretch to cars where the reverse is the case.

Eh? I was saying that more cars make people more aware of cars and less
likely to have accidents with them.

No you were saying that there were so few cars around that unfamiliarity
with cars was the reason why accident rates rose year on year as traffic
increased.

"Because it hadn't reached the critical mass of numbers to be safe in
during the first half of the 20th Century. Cars were not a completely
normal thing of which everyone was aware and constantly on their guard
as is the case now"

And back to the wiki, "Traffic
engineers observe that the majority of drivers drive in a safe and
reasonable manner, as demonstrated by consistently favorable driving
records.

Now who was it who said?:

"But as the record shows, you won't get them them acting responsibly by
assuming they'll sensibly limit themselves."

A report from the British Columbia Ministry of Transportation
includes in its summary the finding that the incidence of crashes
depends more on variations in speed between vehicles than on absolute
speed, and that the likelihood of a crash happening is significantly
higher if vehicles are traveling at speeds slower or faster than the
mean speed of traffic." (ref of
http://www.th.gov.bc.ca/publications/eng_publications/speed_review/Speed_Review_Report.pdf
given).

So, you have lots of cars travelling at a similar speed (like, say, a
speed limit or roundabout it) and you have fewer accidents than everyone
setting their own pace.

Which is why the 85 percentile limit makes some sort of sense and why a
good many countries have minimum limits as well as maximum limits. Here
in the UK the notion that a slow driver is a safe driver is king and
although there is legislation on the books for minimum limits I don't
think there are any. I certainly have never seen a minimum limit.

The wiki also makes the point that drivers tend to ignore inappropriate
limits. The motorway limit may be below the 50 percentile mark
regardless of the limit and certainly would be if there was a way of
demonstrating what speeds drivers would drive at if not limited by law
to 70.

I thought you were claiming an equality in punishment. Loss of job,
however painful, is little more than a slap on the wrist compared with
incarceration which, most likely, also has loss of job on the
specification ***.

But I wasn't claiming that, whatever you thought.

No. Aside from anything else, it /isn't/ easy to know how fast is fast
enough. The evidence is there in the casualty figures.

Most accidents are a slow speed.

I didn't say "accidents", I said "casualties". Not nearly so many
casualties at lower speeds.

Less severe injuries but even lower speed crashes (IIRC 95% at 45 mph or
below) result in casualties. And in any event dv/dt is the significant
factor, not v per se.

You are most likely to fall asleep doing something that is relatively
undemanding. I sometimes drive when I am too tired and it is easy to
fall asleep wombling along in a convoy with nothing to do but follow the
vehicle in front. I know when I get to the stage of no longer looking
out for overtaking opportunities I had better start looking out for
somewhere to park up for a rest.

It varies highly between individuals. If I'm starting to get tired I'll
come off the motorway and take a twisty A as I find that keeps me awake.
Roos, OTOH, finds the twisty As far more tiring and thus worse for her
concentration than the motorway as it overloads things. We're
completely opposite in that respect, and it shows it's dangerous to
generalise from personal experience.

IIRC modern road design eschews dead straight roads as they do not
provide enough stimulus even for the wide awake driver at legal speeds.

I had intended to trawl the Internet for speed limits for individual
countries, starting with Germany, but, as is often the case these days,
I immediately ended up with Wikipedia. I commend in particular what it
says about the 85th percentile rule and law enforcement generally, and
would draw Petes attention particularly to what allegedly happened in
Norway when they raised a low national speed limit to a slightly less
low limit.

Have I said that all speed limits need to be lower? Have I said none
should ever be raised?

You have been extolling the virtues of driving below limits and implying
that those who drive faster are irresponsible idiots. Even just above
you are maintaining that slower is safer.

--
Roger Chapman
Nearest Marilyn still to be visited - Great Orme.
89 miles as the crow flies,
considerably more as the walker drives.
.