Influence of internally reflected sunlight on the visibility of vehicle direction indicators with clear lenses

Abstract

There is some concern that vehicle direction indicator lamps with clear outer lenses make it difficult in bright sunny conditions to decide whether the signal is on or not. This study photometrically evaluated, under bright, sunny conditions, both luminance contrast and colour contrast between the on and off states for direction indicator lamps that use either an amber lens or a clear lens. The results indicate that luminance contrast between the on and off states is greater for lamps using an amber lens. On the other hand, the results indicate that colour contrast between the on and off states is greater for lamps using a clear lens. Because luminance contrast is likely to be the primary variable influencing driver performance, these results suggest that using clear-lens direction indicators is likely to make it more difficult to determine, in bright, sunny conditions, whether the signal is on or not. However, the magnitude of the decrement in real-world performance with clear-lens signal lamps remains to be ascertained. (A)