This paper presents the results of two studies carried out to ascertain whether flashing lights, placed on or near road signs actually impairs sign legibility. In the first study, two types of equipment, discharge lights and conventional incandescent flashing lights, were compared by measuring the reading distances of signs equipped with these two types of light. The results of the study did not reveal significant differences among the reading distances obtained with the various configurations. The second experiment was carried out using only discharge lights of different powers. The same experimental procedure was repeated. In addition to measuring the reading distance, the discomfort experienced by the observers was assessed. A subjective scale of discomfort with five levels from "no discomfort" to "extreme discomfort" was used. The main result is that the "discomfort index" thus obtained varies significantly with both the number and the power of the discharge lights, whereas the reading distance only varies with the number of lights. This corroborates the hypothesis of discomfort glare.
Samenvatting