Tunnel lighting: the difference between day and night

Tunnel lighting requirements during the day when the brightness of the driver to drive to the tunnel adjacent segment determines the brightness adjustment of the eyes in the tunnel section of the threshold requirements, it should consider two kinds of adjustment of brightness: adjacent segment brightness and equivalent brightness, sky brightness. At the end of the tunnel safe braking distance at the driver, which is close to the minimum length of the section, feel close to 1/4 is equal to the height of the tunnel brightness at the bottom of the center, with eyes for 2X100 cone vertex.

Tunnel lighting during the day in general, if from the entrance before the safe braking distance to see the past, most exports view, is a tunnel or underground passage without additional daytime lighting (relative to the normal lighting at night).

On the contrary, if you look at the past from the same position, the exit in the black box, where obstacles, such as the car may hide it, then you must provide daylight lighting.

At the end of the tunnel safe braking distance at the driver, which is close to the minimum length of the section, feel close to 1/4 is equal to the height of the tunnel brightness at the bottom of the center, with eyes for the average brightness of 2X100 vertex cone view range.

External factors close to the brightness brightness are very different in different tunnel: mountain tunnel, the tunnel surrounding mountain brightness determines the basic brightness close section; underwater tunnel, tunnel entrance at the top of the sky brightness effect on brightness close to the tunnel section; viaduct ground tunnel and underground structure, shape close brightness depends in part on the building, part of the upper part of the sky depends on the brightness; and in the buildings, the sky has little effect.

Most of the tunnel type, can take various measures to reduce the brightness close to the section, such as the use of rough dark material to deal with close to the section of the road, the tunnel inside and near the mouth of the tunnel wall (such as underwater tunnel); and in the adjacent place above the entrance entrance or planting trees to shelter the bright sky, or tunnel built as far as possible tall, which can reduce the brightness in the tunnel for energy saving.

Tunnel lighting for night lighting, entrance lighting reduced, while the outlet section, the tunnel lighting inside the tunnel lighting is lower than that in the night there will be a "black hole" phenomenon, therefore, should set the transition section, gradually reduce the lighting level until it reaches the external road lighting level.