In tunnel design, tunnel lights are divided in three categories: enhanced lighting fixtures, basic lighting fixtures and emergency lighting fixtures according  their functions. The light distribution design of these 3 types of lamps should be different. At present, common light distribution forms include concentrating light distribution, side-emitting light distribution, Lambertian light distribution, and bat wing light distribution.

　　The brightness requirements for the entrance section and exit section of the tunnel are relatively high, and the road between the lights is small, and some are only 1~2m. When designing the light distribution of lamps, what needs  be considered is how  enhance the brightness of the road surface. At the same time, it is also necessary  consider the brightness and uniformity of the interior of the tunnel. Therefore, the brightness of the enhanced lighting fixture cannot be a bat-wing type light distribution or a Lambertian type light distribution, but a concentrating type light distribution or a side shot type light distribution should be used. In the middle section of the long tunnel, the distance between the lamps is relatively large, 4~6m. When designing the light distribution of luminaires, what needs  be considered is the brightness and uniformity in the tunnel. Therefore, the light distribution of the middle section lighting luminaires should not be positive or side-lit, but should be bat-wing or Lambertian. Light distribution. For tunnels longer than 1000m, an emergency lighting system must be installed, and the lighting interruption time shall not exceed 0.3s, and the maintenance time shall not be less than 3min. When emergency lighting is started, the brightness of the road surface in the tunnel shall not be less than 10% of the intermediate brightness and 0.2cd/㎡ Therefore, the emergency light has a large space between the lights, up  8~10m, and the emergency light distribution design should be a bat wing.