Evaluation on Lighting Condition and Visual Legibility of Road Surfaces and Traffic Signs in Bandung City

As the capital city of West Java Province, Bandung has been growing fast nowadays, which increases the number of road users, during day and nighttime. In order to assure road users can drive safely at nighttime, good visual condition of the road surfaces and their traffic signs is required. The main objective of this research is to evaluate lighting condition and visual legibility in some roadways in Bandung, by determining average luminance, overall uniformity, longitudinal uniformity, and luminance coefficient of road surfaces and traffic signs, and comparing with the minimum criteria. Software was used to simulate the lighting condition of the roadways and to optimize the lighting parameters. Laboratory experiments were conducted to investigate visual legibility of some common traffic signs, based on luminance contrast of the traffic signs’ material. Generally, lighting parameters of the observed roadways had not fulfilled the minimum standard recommended by the Illuminating Engineering Society of North America. Concrete surface was also found more reflective (average luminance coefficient of 0.05 cd/m2/lux) than asphalt one (0.04 cd/m2/lux). Laboratory results show that most traffic signs in Bandung were made of advertising grade material, whose average luminance contrast values ranged from 2.33 to 2.85, which were still below the American Association of State Highway and Transportation Officials M.268-77 standard which states traffic signs at least must be made of engineering grade material.