Abstract
Of the most customary types of signal lights for trams and buses - all in the "negenoog" (nine-eye) design - the technical properties related to light together with perceptibility in field conditions have been studied. The amsterdam model appeared to be the best starting point for further improvements. Suggestions for these improvements have been made and also predictions of the performance of the amsterdam model after revision. The improved design conforms to the requirements of the highway authorities. The report ends with recommendations for official technical and constructional specifications to be made and also gives directions for practical use.