serious impairment of the conspicuity and legibility of the sign, particularly as seen by artificial illumination. It is also important that the illuminating equipment be serviced adequately so that a reasonably uniform standard of performance may be maintained.
Where signs are unavoidably placed close to hedges, trees or roadside banks, the highway authority should take steps to ensure that the latter are kept trimmed, so that visibility of the signs is not impaired.
Lettering on traffic signs
21. The type of lettering used on traffic signs (reproduced i in Appendix I of this Report) was adopted by the 1933 Committee upon expert advice, and we see no reason to depart from it. Such criticism as has been expressed 1S principally due to the form of lettering not being strictly adhered to, and we suggest that when placing orders for signs authorities should pay special attention to this point.
Siting of traffic signs
22. Except where the character of the sign obviously requires otherwise, all roadside traffic signs should be erected on the near side of the road from the point of view of drivers who are intended to see them. Exceptions are: “Keep Left,” “ Pass either side,” and signs restricting waiting, or indicating the location of an official car park. In the case of “No Entry” signs an additional sign should be erected on the offside of the road. At junctions on dual carriage- way roads having cycle tracks and service roads, it may in some cases be necessary to place signs on the central reservation to face traffic approaching from the side road.
On open roads, warning and informative signs should normally be placed at not less than 150 yards in advance of the places to which they apply, unless the physical conditions at the site (e.g. the presence of a bend-or of another road junction within that distance) make it inadvisable to do so.
In special cases it may be desirable to erect an advance warning sign, consisting of the appropriate standard warning sign with the addition of a plate giving in yards the distance ahead to the point at which the specific danger may arise.
Signs should be erected so as to provide adequate clearance between traffic on the carriageway and the nearest edge of the sign, taking account of the effect of camber on the carriageway. Normally for such clearance a distance of 18 in. from the edge of the carriageway to the nearest edge of the sign should suffice. In order to reduce obstruction on the footpath to the minimum, signs should be fixed to telegraph poles, tramway standards, lamp-posts, etc., and (by means of brackets or otherwise) to boundary walls and private structures where this can be done without loss of efficiency.
In siting traffic signs, consideration should be given to the effect on the conspicuity of the sign of the background against which it will be viewed, and to the possibility, in appropriate cases, of improving conspicuity by the provision of an artificial background.
Height of traffic signs
23. The ideal height of the centre of a traffic sign is at the eye level of the persons most concerned with its message. In open country the lower edge of signs intended for the warning or guidance of vehicular traffic should be 3 ft. 6 in. above the level of the crown of the road. In towns or other places where signs of this height are liable to be obscured or to cause obstruction to pedestrians, it will be necessary to allow a clearance of 6 ft. 9 in. above ground level.
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