The Guide is concerned with photometric and colorimetric matters that are
related to the design of road traffic lights. Its main purpose is to provide
a basis for relevant national standards and codes of practice, but it should
also be of direct use to road traffic authorities and manufacturers of the
lights. It is derived from the CIE Technical Report "Light Signals for Road
Traffic Control", Publication CIE No. 48 (TC-1.6) of 1980, which contains the
experimental evidence on which the Guide is based. The Guide has taken account
of more recent findings, but essentially it is a supplement to Publication
No. 48.
The visibility of a signal light depends on many factors, the most important
of which are the colour, luminous intensity and luminous intensity distribution
of the light. The Guide deals with these factors as well as with various
symbols and t'cut-out'f figures that are used with traffic lights, but the
serious problem of sun phantom, which can affect the correct recognition of a
light, is discussed only briefly. Also, mention is made of some of the design
considerations for traffic engineering.
The term "road traffic light" is used throughout the Guide in accordance with
the CIE International Vocabulary, and it supersedes the earlier term "light
signal for road traffic control".