In message . 170, at
21:19:04 on Sun, 27 Nov 2005, Adrian remarked:
Endymion Ponsonby-Withermoor III ) gurgled happily, sounding much
like they were saying :

Following from the Tower Bridge thread, can anybody explain to me the
logic that "unsigned roads are subject to a 30mph limit" ?

I sort of remember this from when I took my driving test some 20+
years ago but thought it was stupid (and ambiguous). However, I keep
reading reports of people have been prosecuted for allegedly going too
fast where no speed limit was posted.

How can this be ? As far as I am concerned, whenever I see a speed
limit sign facing me, that speed limit is in force until I see another
one (lower or higher than it), right ?
(Obviously, some signs get vandalised and obscured)

but what on earth constitutes an "unsigned road" ? How far does one
have to travel on a road without seeing a sign, before declaring it
"unsigned" ? I seem to remember that this "default 30mph limit" only
applies (a) in urban areas, (b) where the street lamps are 185m
apart.

If I see a 50mph sign, travel for several km at say 47mph, and
an urban area (discuss definition) shows up, does that mean I have
to slow to 30mph. How do I know when I can speed up again ?

This seems a very poor definition.

Is it something like the NSL marker where, (for an ordinary car)
wherein the speed limit automatically changes 60/70 as the road becomes
single/dual carriageway ?

Repeater signs.
From the bottom of the speed limit table in HC103 - "The 30 mph limit
applies to all traffic on all roads in England and Wales (only Class C and
unclassified roads in Scotland) with street lighting unless signs show
otherwise)"

Although you need to be careful as to what constitutes "Street
lighting". Having a few lights along the edge of the street may or may
not be "street lighting". It depends how far they are apart, and how
long a stretch of road is illuminated.

Basically, all speed limits except the default must have repeaters every so
often. If they aren't there, then the default applies, regardless of the
last "big" sign. That's 30 if there's streetlights, NSL (60 S/C, 70 D/C) if
there aren't. Motorways are default 70, streetlights or not.

There are many places on roads where NSL applies, and upon which you can
encounter isolated junctions with street lighting (it often happens
where an unlit bypass has a junction with the "old" road through a
village). But they rarely trigger an automatic 30mph limit for that
short stretch of the road.

--
Roland Perry

In message , Roland
Perry writes
There are many places on roads where NSL applies, and upon which you
can encounter isolated junctions with street lighting (it often happens
where an unlit bypass has a junction with the "old" road through a
village). But they rarely trigger an automatic 30mph limit for that
short stretch of the road.

That's an aspect which still has me confused, and I've seen a good many
more of these recently. I agree that they are rarely marked with
explicit 30 mph limits, but if there are two or more street lights with
less than 200 yards separating them, doesn't that mean that they
automatically impose a 30 mph limit? It sounds as if you think not,
but I'd be grateful for a fuller explanation of why you think that.


--
Clive Page

In message , at 23:30:26 on Mon, 28
Nov 2005, Clive Page remarked:
In message , Roland
Perry writes
There are many places on roads where NSL applies, and upon which you
can encounter isolated junctions with street lighting (it often
happens where an unlit bypass has a junction with the "old" road
through a village). But they rarely trigger an automatic 30mph limit
for that short stretch of the road.

That's an aspect which still has me confused, and I've seen a good many
more of these recently. I agree that they are rarely marked with
explicit 30 mph limits, but if there are two or more street lights with
less than 200 yards separating them, doesn't that mean that they
automatically impose a 30 mph limit? It sounds as if you think not,
but I'd be grateful for a fuller explanation of why you think that.

Looking at the rules as expressed on the ABD site - and assuming the
lamps are close enough together (200yds) to make the road officially
"lit":

http://www.abd.org.uk/speed_limit_signs.htm

If the lit section is less than 350m (and the speed limit either side is
40 or NSL), then no repeaters are required. This is difficult to unpick.
However, from the general tone of the rules I believe that it's correct
to assume that such a stretch of road has "missing" 40/NSL repeaters,
rather than "missing" 30mph signs.

Similarly if the lit section is less than 450m, and the road either side
has a 50mph limit. (Very few roads have explicit 60mph limits, so let's
not worry about that one).

On the other hand:

If the lit section of road is between 350m and 600m long, and has NSL
either side, then one would expect to find a "derestricted" repeater in
the first 250m. The lack of such a repeater would imply the road is
30mph.

If the lit section of road is over 600m long, and has NSL either side,
the first repeater must be within 450m. The lack of such a repeater
would imply the road is 30mph.

[And similar rules for the last two for 40mph, 50mph and 60mph roads].
--
Roland Perry