if the street lighting is switched off or reduced for part of the night. Where there is no street lighting it should be permissible for these signs either to have direct lighting or to be reflectorised.
Turn left and Turn right signs should be internally illuminated at all times.
At all important junctions on Primary roads there should be direct lighting of directional, prohibitory and mandatory signs. It should be left to the discretion of highway authorities to decide whether directional and other important signs should be externally or internally illuminated.
Informatory signs which do not justify the expense of direct external lighting should be placed where they are most visible after dark under the street lighting.
All temporary prohibitory and warning signs and most temporary informatory signs should if possible be reflectorised (paragraph 259).
Reflecting material is greatly superior to reflecting lenses for the illumination of the characters and symbols of traffic signs. Reflecting material should be used to illuminate the whole background of all unlit black on white directional signs. Partial reflectorisation is not satisfactory (paragraph 260).
Tubular fluorescent lamps should more often be used to illuminate the larger signs. These should be mounted below the sign but if risk of interference exists they should be mounted above it (paragraph 262).
British Standard No. 873 should be reviewed without delay (paragraph 262).
Sign lighting lanterns should be mounted so that distracting stray light is not shed behind the sign and so that they avoid, as far as possible, casting shadows. on the face of the sign in sunlight (paragraph 263).
The correct distance between a sign and its junction will depend on vehicle speeds and road conditions. New signs should be mounted at the distances indicated in Appendix VII (paragraph 264).
Where a Reduce speed now plate is necessary beneath a roundabout warning sign this should be placed on the central reservation 500 yards from the roundabout and be repeated at 440 yards on the nearside verge (paragraph 266).
Signs should be mounted as far as possible at the eye level of the driver of an average private car. Their lower edge should be 3 to 5 feet above the highest point of the carriageway.
When a sign is liable to be obscured by, or to obstruct, pedestrians it should have a clearance above the ground of 6 feet 9 inches (paragraph 268).
Clearance from the edge of the carriageway should never be less than 1 foot 6 inches in urban areas and 4 feet on high-speed dual-carriageway roads (paragraph 270).
Signs should be so sited that they are not obscured by tree or hedge growth (paragraph 271).
If a sign is liable not to be seen against its background it should be given a special surround (paragraph 271).
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