Evaluation of the impact of road sign material on the occurrence of dew

Under specific conditions water vapor condensates on traffic signs (dew), resulting in deterioration of retroreflective properties of the reflective film. The dew is visible in the form of black patches, which may render the sign illegible. The objective of the presented research was to limit dew formation through the use of materials with various thermal conductivity and determine the impact of material on intensity and speed of condensation. The tests were performed at a field test site, using traffic sign blanks made of various materials. Each sign was divided into 4 sections, using 2 types of retroreflective films (in 3 colors) with or without anti-dew film. The occurrence of dew was recorded by performing serial photographs of each sign. Luminance, coefficient of retroreflection and temperature distribution were measured and analyzed in terms of their changes in time. The results of the research confirmed that at the chosen field test site the impact of the materials on the intensity of dew formation was insubstantial.