Velvet wrote:
JNugent wrote:
Velvet wrote:
[ ... ]
... If you want to discredit speed
limits, then give examples of where they're set too low or too
high, rather than criticising signing policy.
How about 40mph on the M4?
And no, I am not referring temporary limit at a set of roadworks
(even though 40 is still extracting the urine a bit, even at
roadworks). I am speaking of a permanent limit of 40mph on part of
the M4.
Do you not agree that such a limit is *way too low* on a motorway?
And exactly where is this 40mph on the M4? Perhaps where it passes
through a built up area in London, where the lanes are narrow and it
twists with frequent junctions?
I don't know what you are trying to imply, but a motorway passing
through a "built-up area" is entirely separate from the local road
network. Think of the M6/M5 in NW Birmingham, Dudley, Walsall, etc.
Perhaps you think they should be limited to 40 as well?
That depends on the local circumstances. Having also driven that
several times, I would say it is possible that it should. It can get
very busy, and have long queues in one (or more, but often one) lane
as people attempt to join/exit the motorway, with faster traffic in
the other two. I have seen nasty near misses where people attempt to
queue jump, and try and join the faster moving lanes from the
queueing one, then cut back in later on.
Are you *really* saying that a 15 mile stretch of the country's premier
north/south route should have a 40mph limit?
The Chiswick Flyover's lanes are exactly the same width as any other
motorway lanes (12' wide). It doesn't have hard shoulders, but then,
neither do a great many 2 x 2-lane d/cs limited to 70mph - so of
what relevance could that be?
Possibly the fact that it is:
a flyover. Some vehicles can end up over/through bridges and on the
road below that they span - or has this not occurred to you? I've
actually seen that happen.
So do all flyovers have a 40mph limit?
Or - in your world - *should* all flyovers have a 40mph (or lower) limit?
If not, why that one (which was designed and built to have no speed limit at
all)?
no hard shoulders - on a road as busy as that, it is inevitable that
breakdowns and accidents occurr. As such, there is no way to get cars
out of the main lanes, and the impact on traffic is severe, causing
queueing, and approaching such a situation at 70 can be very
dangerous, approaching at 40 takes away some of that danger though
not all.
So should all greade-separated, motor-traffic-only, dual-carriageways
without a hard shoulder (and there are a lot of them) have a 40mph limit?
If not, why this one?
queueing - I've seen this many many times on this stretch.
Approaching a queue at 40 is a wholly different situation to
approaching a queue at 70-80, as would happen if the limit was as you
appear to want it, 70.
So, to develop your theme, you are also saying that any route subject to
queuing should have a 40mph limit?
multiple bends leading to restricted visibility - again, a valid
reason for the limit to be lowered.
The M4 does not have "multiple bends". Its alignment was designed for 70mph+
(as are all motorways of the period except for one bend on the northern
reaches of the M5).
short slip lanes onto and off - as you drive this, no doubt you're
aware of the short length that the slip roads parallel the main
carriageways, no? The faster the speed of the traffic on the main
carriageways, the longer the slip lane must be to avoid the problems
where vehicles are unable to merge successfully. This is, as I'm
sure you're aware, exacerbated by the fact that there are no hard
shoulders in which to utilise in this situation - you're faced with
making a dead stop before the concrete barrier gets you, or swerving
out into the side/right in front of someone at the last minute.
So again, any road without hard shoulders - in your view at least - must
have a 40mph limit?
Is that a fair summary of your position?
And as a regular driver, I'm well aware that since the limit was
lowered, there are less accidents on that stretch, and journey times
are more predictable.
"More predictable".
Weasel words for "predictably longer"?
Exactly which ones of the above reasons are you going to disagree
with, I wonder.
Since none of them seem to apply anywhere else (not even in Livingstone's
London - look at the [former[ A40(M) and A102(M), for instance), I wonder
how seriously you can expect any of them to be taken. And your problem is
that none of them have a logical boundary. If the 40mph limit on M4 at
Chiswick/Osterley were justified, then the same limit would be justified on
every dual two-lane d/c in the country which has no hard shoulders and is
subject to peak overload. The non-upgraded sections of the A1, for instance.
Or the A14. Or the A12, or the A10 through East Anglia.
As for "frequent junctions"... there is one junction (where the A4
"becomes" the M4) at the western end and one intermediate junction
(with the N & S CRs). Let's see... that's... er... two junctions.
You'd have to be pretty weird to class that as "frequent", wouldn't
you?
Perhaps I'm thinking of further on, where it becomes the A4,
Irrelevant.
That road has *always* had a lower limit than its motorway continuation.
Motorways have higher speed limits than urban radial routes because they are
safer at higher speeds. That is the reason why motorways (rather than mere
at-grade d/c extensions) are built.
Using your "logic", the M1 should have a 30 limit because it is an extension
of Holloway Road and Baker Street.
but
regardless, the traffic flows better since the limit was set to 40.
Live with it.
"Flows better" is a peculiar interpretation of it. It certainly flows more
slowly. I guess that for some, "slower" is automatically "better".
[ ... ]
Some more information on where your 40 mph limit on the M4 would be
useful in determining whether it is justified and thus not a valid
piece of supporting evidence; or not.
Are you denying that there is a permanent 40mph limit on part of the
M4?
No, please read more carefully.
Since you now claim to know where the 40 limit is, what was your purpose in
asking where it was?
...To the casual reader of
*your* post, you seem to be talking about a stretch of the M4 that is
3 lanes wide with full hard shoulders, that has the same with a 70
limit to each side of it, admittedly this would be a little peculiar.
No, please read more carefully.
I said nothing of the sort. I said that a stretch of M4 has a 40 limit.
And that was correct.
And (more importantly), it is an example of "...speed limits ... set too
low" - remember the orginal context?
By omitting to state where the limit was, or give any other
information on how the road differed from the more common motorway,
you appeared to be attemping to mislead by omission.
Not at all. The Chiswick section of M4 was designed and built to be operated
at no speed limit whatsoever - though it had the national 70 limit imposed
soon after opening.
Since you chose to use the 40 mph limit on the M4, yet omitted to
state *where* it was along the length, it was incumbent upon you to
clearly define where it is, not me.
What difference does it make where it is?
40 is ridiculously low for a motorway.
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