In roadway lighting, researchers and engineers have regarded the silhouette vision as the definite premise of visibility evaluation over 70 years. However, the authors investigated reflection factors of various obstacles dropped on the roadways and found that many obstacles had reflection factors higher than what people had believed in the past. Based on the results, the authors proposed "total revealing power", evaluating the total visibility for not only silhouette vision but also reverse silhouette vision. It was shown, by using this factor, that even if roadway lighting illuminates objects more positively and intentionally, the visibility of the objects will not be declined. This finding allowed the pro-beam lighting system, intending to improve the visibility of preceding cars, to be implemented in the real roadway.
