Total Revealing Power for Tunnel Lighting

We propose adopting total revealing power to evaluate the visibility of obstacles dropped on the road in tunnels. Total revealing power is a combination of silhouette vision and reversed silhouette vision. To evaluate visibility under conditions of total revealing power, we surveyed relationship the revealing power and the reflection factor of an obstacle dropped on the road surface of an expressway. We also carried out experimental observations to determine the relationship between road surface luminance and luminance contrast to achieve a correct perception rate of 75% with silhouette vision and reversed silhouette vision. Results show that the visibility of an obstacle dropped on the road depends on the road surface luminance, in spite of the vertical illuminance. We found that total revealing power is effective in estimating visibility of an obstacle dropped on the road. This is because such than assumed in previous obstacles usually have a higher reflectance factor by Smith.