Abstract
The discussion on the method to determine photometric data of luminous signals has been deepened by new contributions. Available test results offer the possibility to deal with the threshold values and firld factors required for flat signals and especially for road traffic signals, as part of the future work of the committes. Basic rules for the characterization of the lighting values of luminous signals and for the determination of the range of luminous signals will be presented to the Plenary Meeting at Washington to be accepted as official C.I.E. Recommandations.