day three arrows curved to form a circle, but by night a plain circle of reflectors would, in our opinion, be adequate. With this consideration in mind we reviewed the various symbol warning signs, and we believe that our recom- mendations will enable them to be fitted satisfactorily with reflecting lenses. The arrangements of lenses which we recommend are shown in diagrams 1A, 2A, etc., in Appendix VI. The reflecting lenses should never be fitted outside the boundaries of the black on white symbol.
Letters of not less than 3 in. in height can be fitted with reflecting lenses to give reasonable legibility at night when viewed in the light of vehicle head-lamps. On some signs it is not possible to use a minimum size of 3 in. letter without making the over-all size of the sign unduly large, but where practicable our recommendations provide for the using of letters of not less than 3 in. in those words or figures which convey the essential message of the sign.
If not directly illuminated, the red disc over prohibitory signs, the red ring over mandatory signs, the red triangle over warning signs and the triangle and ring symbol over the “Halt” and “Slow” signs, should be fitted with red reflecting lenses. The amount of light reflected by red lenses is considerably less than that reflected by clear lenses of equal quality, but we consider that the striking effect of the red colour is of primary importance.
We recommend that the British Standards Institution should be asked to prepare a specification for the optical properties of reflecting lenses for use in traffic signs. The intention of the Institution to do so was indicated in British Standard Specification No. 873—1939, but the matter has doubtless been delayed by the war.
The recommendations made above are based on the use of circular reflecting lenses, but provided the same reflected outline is obtained we see no objection to the use of other approved reflecting media.
Control of advertising
27. In our view it is most undesirable that advertising signs directly illuminated or fitted with reflecting lenses should be erected in the vicinity of roads in positions where they may distract the attention of drivers from traffic signs or may tend to be mistaken for traffic signs. Highway authorities or local authorities should be given greater powers in this direction than they have at present. Since the effectiveness of signs fitted with reflecting lenses depends upon their being so placed as to fall within the headlamp beam of vehicles on the road, there may easily be confusion of such signs with standard traffic signs. We consider it essential, therefore, that the use of reflecting lenses or other reflecting media in advertising signs should be prohibited.
Dimensions and lighting of posts on street refuges
28. Our attention has been drawn to the possibility of bollards at refuges being of such dimensions as unduly to restrict the vehicle driver’s view of other traffic, both vehicular and pedestrian, or to prevent pedestrians on the refuge, particularly children, from seeing approaching vehicles. We think it desirable that maximum dimensions should be specified for bollards on refuge islands, and make the following recommendations:
(a) The maximum width of the bollard (other than the portion incorporating an authorised “Keep Left” sign) should not exceed 12 in.
(b) The maximum height of the bollard (including any authorised “Keep Left” sign incorporated in it) should not be more than 4 ft. above the road level, except that, where the provision of a 24 in. × 18 in. “Keep Left” sign is authorised, a maximum height of 4 ft. 6 in. should be permitted.
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