In an experiment four types of overhead guide signs were compared. All signs had high intensity grade retroreflective legends. Type 1 had a painted blue background, type 2 an engineer grade retroreflective background, type 3 a high intensity grade background and type 4 again a painted blue background, but this sign was externally illuminated. The legibility distance of the illuminated sign was 19% higher than that of the non-illuminated signs. No significant differences in legibility were found between the 3 types of non-illuminated sign. With high beam headlights all four types had about the same legibility distance. The recognition distance of all types was at least 470 m. It is recommended that non-illuminated overhead signs are only used on fairly long sections of highways in remote areas. (Author/publisher).
Samenvatting