of street lighting, and moreover that the matter needs to be considered with regard to conditions throughout the country and not merely in the Metropolitan Area. We have therefore been asked to include it within our purview.
105. It may be convenient if we quote the recommendations referred to above. They are as follows:
(i) the colour of the post should be white outlined with black, and during the hours of darkness the posts should be illuminated by white flood-lighting;
(ii) the horizontal angle of illumination of the post should be at least 120° and the projected width (i.e. the width as seen by a person directly facing the post) of the illuminated surface of the guard post facing approaching traffic should be not less than 5 in.;
(iii) the post should be illuminated for a vertical distance of not less than 2 ft. and the upper edge of the illuminated portion should be not less than 3 ft. and the lower edge not more than 18 in. above the road level;
(iv) the height of the post should be a minimum of 4 ft. above the road level, but the height at which the light should be placed is immaterial so long as the requirements in (iii) above are observed;
(v) it is not essential that the head of the post should be illuminated, but if a light is provided it should be white. and should be diffused by suitable glass.
106. We endorse these recommendations, except that (i) should be interpreted to include internally illuminated panels as well as white reflecting surfaces, but consider that they should be supplemented as follows :
(a) Guard posts should be so designed and illuminated that they are readily identified as such and are clearly visible to motorists and other road users; care should be taken to ensure that pedestrians making use of the refuge are not obscured by the guard posts.
(b) Self-luminous posts are in general to be preferred to those which depend for their visibility on extraneous lighting.
(c) The posts should be rendered luminous by concealed sources placed (preferably) at the top. The luminous portion should extend to as near the bottom of the post as possible, and the brightness should not fall away appreciably towards the bottom. The posts should be luminous on all sides except those facing towards the middle of the island.
(d) The average brightness of the luminous portions should be about 8 equivalent foot-candles with a variation over the whole surface of not more than 4 to 1. Our investigations have shown that a brightness of this order is adequate for roads lighted to either Group A or Group B level, and at the same time is not so high as to produce undue glare.
(e) The kerb of the refuge should be of a material which is naturally light in colour or should be painted white periodically, whilst the light from the posts should illuminate the kerb and preferably throw the vertical sides into sharp relief.
(f) One self-luminous post should be placed at each end of the refuge and there should be a central post fitted with a light source surrounded by a diffusing globe at a height of about 16 ft. This source is intended to serve as an indication of the presence of the refuge to drivers whose view of the guard posts may be obstructed by other vehicles; it is not intended to enhance materially the visibility of, e.g. pedestrians on the refuge, which is a matter for the street lighting installation.
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