1、BRITISH STANDARD BS1376:1974 Incorporating Amendment No. 1 Specification for Colours of light signals UDC656.05:654.912.5:628.975:535.6BS1376:1974 This British Standard, having been approved by the IlluminationIndustry StandardsCommittee, was published under the authority ofthe Executive Boardon 30
2、September 1974 BSI 04-1999 First published April 1947 First revision January 1953 Second revision September 1974 The following BSI references relate to the work on this standard: Committee reference LGE/17 Draft for comment72/24493 ISBN 0 580 08427 2 Cooperating organizations The Illumination Indust
3、ry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: The Government departments and scientific and industrial organizations marked with an asterisk in the
4、 above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Association of Public Lighting Engineers Illuminating Engineering Society British Glass Industry Research Association Institution of Electrical it relates onl
5、y to the colour of the light emitted by the signal and is in no way concerned with the method used to obtain this coloured light. Although the colours complying with the requirements of Section2 are properly defined as signal red, signal green etc., the work “signal” has been omitted for ease of rea
6、ding in much of the text of this standard. Section3 deals with light sources, filters and combinations of these which may be used to produce coloured light to the requirements of Section2. Some general guidance relating to problems of the stability of the signals and colour filters is contained in A
7、ppendix A. Section4 deals with photometric procedures by which complete light signals and filters may be tested for compliance with this standard. A means of inspection, which may be convenient when dealing with large numbers of filters, is described in Appendix B. Appendix D gives information on th
8、e requirements and recommendations of a number of international bodies for the colours of light signals. It is normally sufficient for purchasers of complete light signal equipments to specify the required colour and class, in accordance with Section2 and the intensity and distribution of the light
9、output required. The inclusion in such specifications of additional requirements for specific light sources and filters may impose unnecessary restrictions on the design and method of manufacture and should be avoided if possible. The content of Section3 should not, therefore, normally form a part o
10、f the specification of a complete equipment but may be regarded as an indication of what can be achieved with various combinations of filters and light sources and as guidance to designers and manufacturers in meeting a particular requirement. However, Section3 may be used as a specification for rep
11、lacement light sources and filters and in those cases where a purchaser has a particular reason for including such detailed requirements in a specification for a complete item of equipment. Section 2. Colours emitted by light signals 5 General When coloured lights are fixated and only just visible t
12、hey appear nearly colourless, with the exception of red. As they get brighter, green lights become recognizable, thus providing the common three colour system of red, green and an intermediate colour which, at still higher luminosities, becomes distinguishable into yellow, white or blue. These consi
13、derations have dictated the choice of colours of signals that are frequently seen near the limits of visibility but in order to preserve the similarity of message that each colour conveys, the use of these colours has naturally spread to signals that are normally only seen at close range. In multi-c
14、oloured signalling systems it is possible to improve the certainty of colour recognition by ensuring that any pair of colours which must be distinguished are as far apart as possible in chromaticity, consistent with their having adequate intensity. For this reason, this standard subdivides each of t
15、he main signal colours so that appropriate colour areas can be chosen where high differentiation is required. The use of blue as a light signal colour must be treated with some caution. Confusion of blue with other colours may occur unless the illuminance produced by the light at the eye of the obse
16、rver (thepoint brilliance) is substantially above threshold. Since the luminous efficacy of radiation in the blue region of the spectrum is low, it is difficult to ensure adequate illuminance except at short ranges. Furthermore, colour recognition is uncertain if the angular subtense of the light at
17、 the observer is too small, say less than about10 minutes of arc. It should also be noted that, owing to a yellowing of the lens of the eye with age, older observers may have elevated thresholds for detection and recognition of blue light.BS1376:1974 BSI 04-1999 3 6 Ranges of colours In this standar
18、d, a colour of class A has the widest range of chromaticities and embraces the more restricted ranges designated classes B and C. Where two coloured lights need to be distinguished with extra reliability by observers with normal colour vision they should be chosen from their respective restricted ra
19、nges so that they are separated as much as possible in the CIE chromaticity co-ordinate diagram (see Figure 1). For example, class C white and red lights are distinguished from a yellow light with more reliability than are the class B whites and reds which, in turn, are more readily distinguished fr
20、om yellow than the whites and reds permitted by class A. 7 Limits of chromaticity of light signals The colour of the light emitted by a signal, when tested in accordance with the requirements specified in Section4, shall lie within the boundaries for the specified colour on the CIE(1931) chromaticit
21、y co-ordinate diagram (seeFigure 1) defined by the equations in Table 1, together with the spectrum locus (except for white) and the purple boundary (for red classes A and C only). The definitive requirements of this standard are in terms of the equations in Table 1 but the chromaticity diagrams of
22、Figure 1, Figure 2 and Figure 3 have been included as illustrations of the various colour boundaries. Figure 1 is a plot of the chromaticity diagram showing all boundaries and Figure 2 and Figure 3 show in greater detail the boundaries for red and yellow respectively. When it is required to plot the
23、 areas of acceptable chromaticity regions on a diagram, it is often easier and quicker to do this by joining points corresponding to the intersections of the boundaries than by drawing the boundaries from their specifying equations. The co-ordinates of these points are, therefore, given approximatel
24、y in Table 1A. 8 Choice of restricted colour limits In choosing the restricted class of coloured lights to be adopted in a multi-coloured signalling system, consideration should be given to the risks of confusion between the various pairs of colours, so that if there is a conflict between several ne
25、eds that which is most serious can be given priority. Also, in certain circumstances it may be necessary to consider the needs of observers with abnormal colour vision. In the majority of cases where the ability to interpret a light signal is important, the individuals concerned will have been selec
26、ted so as to eliminate those with defective colour vision. Where no such selection is possible, as in the case of road traffic lights, the more prevalent classes of persons with abnormal colour vision i.e.those who confuse reds and greens, can be helped by a particular choice of these two signal col
27、ours. This choice would avoid yellow-greens and would select blue-greens rather than mid-greens and would also select reds with a substantial yellow component rather than darker reds. Thus, the use of a class B red together with a class C green would provide many such persons with a certain amount o
28、f colour distinction between these two signals, where they would otherwise have to rely for identification solely on the position of the light within the signal head. For some purposes, the y=0.3 dark limit of class B red may be irrelevant and the appropriate range of chromaticities may be specified
29、 as B+C. Table 2 gives typical applications of colour classes of light signals to the various branches of transport. 9 Colour stability Having decided upon the chromaticity limits for a particular light signal application, it is a normal requirement that the colour should remain within these limits
30、throughout the working life of the signal and in all its anticipated conditions of usage. The colour of the light emitted depends upon the chromatic qualities of the light source or of the colour filter/light source combination and these qualities are in turn dependent upon a large number of factors
31、 which are fully discussed in Section3 and Appendix A. It is important that these factors be fully appreciated by anyone designing or specifying a requirement for a light signal as they may impose limitations on what can actually be achieved in practice. A particular problem arises in connection wit
32、h the dimming of signals, in which the colour temperature of the light source is lowered when the light output of the lamps is deliberately reduced (seeclause19). 10 Effects of the atmosphere When a signal is required for use at long distances in a wide variety of conditions, consideration should be given to the effect that the passage of light through the atmosphere may have on its apparent colour.
