This work is part of a joint UK/French initiative to assess the performance of variable message signs (VMS) in fog and to make recommendations about the usage of VMS in conditions of poor visibility. In fog chamber test facilities, fog was generated and the luminance of the VMS under test was recorded by a luminance meter at various specified distances. Observers were used for subjective tests to assess at which fog density a character displayed by each VMS could be detected and then recognised, again at specified distances. A model has been produced for the luminance output required from a VMS in all conditions of fog density. The results of the experiments show that the level of sign luminance, as seen through fog, is a useful measure of the detection and recognition of a VMS. (A)
Samenvatting