MINISTRY OF TRANSPORT SPECIFICATION
FOR STREET LIGHTING LANTERNS
TO BE USED
IN THE VICINITY OF AIRFIELDS
(1) FOREWORD
A number of Government Departments concerned with flying have powers under the Air Navigation
Acts by which they can require the restriction of lighting in the vicinity of airfields which may
be a danger to air navigation. In so far as street lighting in concerned, the requirements have in
the past been met by the use of cut-off type lanterns, which emit a negligible amount of light
above the horizontal. For such lanterns the British Standard Code Of Practice (C.P. 1004: Part 1, 1952) recommends spacings of
90-100 ft. instead of the 120-150 ft. usual for non-cut-off lanterns. This specification has been
prepared following practical tests to determine requirements, and defines the characteristics
of lanterns which can be employed in the vicinity of airfields where a limited amount of
light showing above the horizontal is permissible, and which at the same time can provide
satisfactory street lighting at spacings commonly employed for medium angle beam lanterns.
(2) GENERAL
The general requirements for construction shall be those laid down in B.S. 1788:1951, "Street Lighting Lanterns", in so far
as they apply. Details of the lantern shall be provided by the manufacturer and shall include a
scale drawing of the lantern, an iso-candela diagram of its light distribution, a statement of the light
output ratio and instructions for adjustment of the lantern at the time of erection. Lanterns may
be of the open or enclosed type. Side or top entry may be adopted.
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The means of supporting the
lamp shall be so designed and constructed that the position of the lamp in the lantern relative
to the optical equipment remains substantially the same throughout the life of the lantern.
If the supports are adjustable a suitable method of locking them shall be provided. The
provisions of this specification shall apply whatever type of light source is used in the lantern.
(3) LIGHT DISTRIBUTION ABOVE THE
HORZONTAL
The intensity at and above the horizontal in any vertical plane through the centre of the
lantern shall not exceed, when the lantern has been erected and adjusted in accordance with
the manufacturer's instructions, the values quoted in the table below.
| Angle from the downward vertical | 90° | 92° | 94° | 96° | 100° | 110° | 120° | 130° | 140° | 150° and above |
| Maximum permissible intensity (Candelas) | 750 | 300 | 95 | 75 | 60 | 40 | 30 | 20 | 10 | 0 |
(4) LIGHT DISTRIBUTION OF GROUP A
LANTERNS BELOW THE HORIZONTAL
The light distribution at angles below the horizontal shall be of the normal medium angle
beam type. For Group A lanterns, the maximum intensity shall not be less than 2,000 candelas,
and shall occur at 75° from the downward vertical with a tolerance of +/- 2° when the
lantern has been erected and adjusted.
(5) ADJUSTMENT OF LANTERNS
Means of adjustment of the lantern after erection shall be provided together with
a device to indicate the angular setting. The indicating device shall be accurate to
+/- ½°
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