Five experiments are reported in which visible distances on the near side of the road were measured in a situation in which two cars meet in the dark: 1) Both cars had full headlights or both dad dipped symmetrical headlights. Full headlights were found to give longer visible distances furring the whole meeting. 2) The same lighting conditions were compared taking signal reflectance into consideration. The higher the reflectance, the greater the difference. 3) The same lighting conditions were compared in simulated hill meeting situations. Full headlights still gave longer visible distances. 4) Symmetrical and asymmetrical dipped headlights of types common in Sweden were compared. As a source of glare in a meeting situation they were equal, although visible distance was considerably longer with the asymmetrical type. 5) Full headlights and asymmetrical dipped headlights were compared. Full headlights gave longer visible distances. These results indicate that the dipping of headlights, while cutting down the discomfort due to glare when cars meet also shortens the distances visible from the cars concerned.
Abstract