The purpose of this report from the CIE Technical Committee 1.6 is to provide information that will be relevant to an understanding of future recommendations on light signals for road traffic control. The report is restricted to matters that are of direct concern to the road user, and it is not concerned with the regulatory status of traffic light signals. There is firstly a review in general terms of subjects related to the visual effectiveness of the light signals attention, perception, vision, factors adverse to visibility, and traffic engineering. In spite of the complexity of the traffic situation and the driving task, agreement can be reached on the colorimetric and photometric requirements of the signal lights. Many investigations have been made into the factors likely to influence the detection of signals, and their conclusions enable suitable specifications to be written for signal lights with regard to colour, luminous intensity and luminous intensity distribution. Although a signal may be capable of generating a visual response in a driver, he may not be aware of it owing to various distractions. Clearly, traffic engineering must be considered in association with the specifications for the lights in order to minimize the decision-making demands on a driver approaching signal lights, and, furthermore, care must be taken in positioning the lights in relation to the driver's field of view. The report also comments upon the problems of sun phantom, and the shape and sues of symbols used with lights. The last section puts some suggestions for specifications for light signals for road traffic control.
Abstract