When providing construction and maintenance zones with traffic control devices use can be made of illumination. Some important elements of this illumination may be: external illumination of traffic signs, yellow flashing lights and the permanently burning lamps (bull-eyes) on the delineation barriers. In the present study the necessity of using illuminating elements when considering traffic safety is investigated. A short description is given of the functions of the traffic control devices at work zones. From these functions criteria are developed with regard to the required detection and/or recognition distances of the traffic control devices. Conditions of clear weather as well as moderate and dense fog are taken into consideration. Recognition and detection distances of particular traffic signs and other devices (illumination) were measured in a field study during clear weather as well as fog conditions. Results of field experiments and calculations in terms of recognition and detection distances are discussed in connection with the developed criteria. In the discussion distinction is made between types of road and types of work zones. In most conditions the illumination appears to be a necessary element with regard to the perceptibility of the traffic control devices during dense fog at night. The illumination of the delineation barriers will be evaluated in a further study.
Abstract