Speed Limit Signage Requirements

Dear Department for Transport,
There is a certain ignorance amongst the general public about the
road standards that should apply in the U.K for MOTORCARS.Recently
I requested a FOI which was fulfilled by Sally Dutton,Senior
Engineer,Traffic Management Section and the reply was absolutely
excellent and will allow me to educate my local council.This is the
quality service the public expect and deserve.
ONE OTHER ISSUE which I would appreciate clarifying is the issue of
speed limit signage.I know that NO signage is required along NORMAL
ROADS(NR) road where street lighting is in place, as it is 30mph by
default, or on open country roads(OCR) or motorways(MW) where it is
National Speed Limit by default.If a different speed limit is in
force then signage must be in place at the START of the change and
repeaters ALONG the length of the affected route, and of course
DIFFERENT standards may apply depending on the speed applicable
because visibility may be difficult at speed or the changes
temporary due to road works.
QUESTION ONE.If a 30mph NR changes to 40mph what SIZE of sign
should be displayed at the START each side and must they be
illuminated? Along the 40mph section what SIZE must the repeater
signs be and how frequently should they be repeated over a length
of 2 miles?
QUESTION TWO.If, due to roadworks,a 40mph NR is temporarilary
reduced to 30mph what SIZE should the temporary 30mph signs be at
the start, must they be illuminated, and what size and how frequent
should the repeater signs be?Presumeaby no repeaters would be
required over a very short length, but are contractors advised of
the standards and how is this achieved? Should the conflicting
40mph signs be covered up or painted over, and restored after
completion of works?
QUESTION THREE.If a section 40mph NR is permanently reclassified as
30mph what are the requirements,as before, of sign size and
illumination at start of change, and 30mph repeater requirements
each side along the length?
QUESTION FOUR.Motorways(MW) must be subject to different
standards.If a MW speed is TEMPORARILY reduced to 40mph due to
roadworks what are the requirements,as before, of sign size and
illumination at start of change, and 40mph repeater requirements
each side along the length?Should the limit change be suddenly from
70mph to 40mph, or done in recognised stages for reasons of
controlled deceleration?Also are there guidelines about the
visibility of these signs, such as positioning in relationship to
the carriageway?What is the reference manual which provides
guidance?
QUESTION FIVE.If a MW speed section approaching a tricky junction
or city is PERMANENTLY restricted to 40mph what are the
requirements for sign size and illumination requirements at the
point of change, and the requirements for repeater size and
frequency?Should the limit change be suddenly from 70mph to 40mph,
or done in recognised stages for reasons of controlled and safe
deceleration?
QUESTION SIX.During roadworks on MW or NR what would be considered
the MAXIMUM length of coned off area or works that could be
acceptable to exist without the need for a repeater sign before
`works end`sign?
Although this FOI may appear complicated it only requests
clarification on the legal requirements regarding the posting of
speed limits.I would appreciate individual answers to each specific
question NOT just reference to a DfT document as the standards for
signage, especially by temporary contractors, causes me some
concern and should be easy to understand.For simplicity this
request relates only to roadworks lasting at least one week.

Yours faithfully,

Dennis Fallon