Abstract
Two studies were conducted to evaluate the visual discomfort that flashing discharge lights can cause when they are used to enhance the effectiveness of signing. These studies compared the reading distance of a signal, a Landolt ring, presented successively with flashing discharge lights and flashing incandescent lights of variable power. A discomfort index was determined by recording the observers' impressions. The subjective factor - the discomfort index - increases with luminous intensity. It therefore seems that the discomfort is subjective and corresponds to discomfort glare.