Roland Perry wrote:

That is not the way people normally describe the "30 mph limit where
there are street lights". If it needs a sign, as well as the existence
of street lights, why do people continually refer to a rule which says
that all you need is street lights?


Because if starting your journey in an urban area (or in the middle of
nowhere for that matter) you may drive a long way without the speed
limit changing. If there are periodic repeater signs, then it is
obvious what the speed limit is. If there are none then it must either
be the national speed limit or the urban 30mph and you must make your
own judgement by taking note of your surroundings.

Speed limits other than the national speed limit or the urban 30mph
require a Traffic Order which will include a definition (in words
and/or on a map) of the affected length of road.

I think the bit of road I'm describing is one that might (or might not)
come under the "urban" definition. If the definition is all about street
lights, and there's part of the definition which says, in effect, you
need more than (say) 500m of street lights before the "urban" definition
is triggered: What happens when a road has 400m of street lights, a lit
roundabout (say 100m), then another 400m of street lights? Is that three
roads of 400m, 100m, 400m, none of which is "urban"; or is it one road
of 900m all of which is then "urban"? [I will ignore the fact that this
is all in open countryside.]

If you have not passed any speed-limit signs then I reckon the national
speed limit applies throughout. However you would, of course, be
reckless to drive at 60mph through the roundabout and could therefore
be guilty of another offence if you tried.


ps Does anyone have a link to the current version of the document where
things like the "500m" above are defined?
--

I think the other person who said it is 200 yards (or the metric
equivalant) is correct.

However, the Road Traffic Regulation Act 1984 can be found on the HMSO
website.
Traffic Signs Regulations and General Directions are somewhere on the
Department for Transport site.
The relevant chapter (Regulatory Signs) of the Traffic Signs Manual is
unfortunately not yet on line.

All the above are lengthy, complex and full of legal and technical
jargon. However, a good article, quoting from them all, can be found
on the Association of British Drivers website at:
http://www.abd.org.uk/speed_limit_signs.htm

ABD believe a greater use of 30mph repeater signs should be used in
places where, although there may be street lamps, it is not so obvious
that the urban speed limit applies. I agree with that although I also
believe 30mph repeaters in every residential road/shopping street etc
would be an unnecessary waste.