Safety Analysis for Illumination Design at Tunnel Entrance and Exit

The illumination design is an important factor affecting driving safety at tunnel entrance and exit. By analyzing lightness change character and visual adaptation mechanism at tunnel entrance and exit, the lightness transition index has been developed. Due to the shortage of accident statistics at tunnel entrance and exit, indirect analysis method was adopted and operating speed difference was selected as medium index to evaluate driving safety. Based on theoretical and statistical analysis, the relation between lightness transition index and operating speed difference at tunnel entrance and exit has been modeled. At last, the recommendation for designing safer lightness transition condition at tunnel entrance and exit has been discussed.