- As motorists approach tunnels, they can have trouble detecting low-visual-contrast objects as the result of glare, discrepancies in illumination, and the process of visually adapting to the tunnel entrance. Table 21.3 contains high-level guidance for initial luminance design, but calculations need to be refined once the tunnel design is better defined.
- When traveling at higher speeds, motorists have less time to adjust their vision to the darker conditions in a tunnel. In these situations, tunnels require more intense illumination to maintain sufficient visibility. Similarly, when more sky is visible in motorists’ field of view upstream of a tunnel or bright surfaces surround a tunnel entrance (e.g., large retaining walls, rocks) more illumination in the tunnel is needed.
| Table 21.3 Recommended Daytime Maintained Average Pavement Luminance Levels in Tunnel Threshold Zones | ||||
| Approach Characteristics | Traffic Speed | Driver Direction | ||
| mph | North | East-West | South | |
| cd/m² | ||||
| Open Road | 60 | 250 | 310 | 370 |
| 50 | 220 | 260 | 320 | |
| 40 | 180 | 220 | 270 | |
| Urban Tunnel | 60 | 320 | 280 | 310 |
| 50 | 280 | 240 | 270 | |
| 40 | 230 | 200 | 220 | |
| Mountain Tunnel | 60 | 230 | 200 | 200 |
| 50 | 200 | 170 | 170 | |
| 40 | 170 | 140 | 140 | |
CONTACT:
Chris VanDyke
Research Scientist | Program Manager
chrisvandyke@uky.edu
