Analysis of Tunnel Lighting
The tunnel is a semi-enclosed space, and natural light cannot illuminate it. The tubular structure of the tunnel determines the difference in brightness between the inside and outside of the tunnel. In order to ensure the continuity of driving and the safety of pedestrians, artificial lighting is required throughout the entire interior even during the day. Tunnel lighting It is an integral part of tunnel construction.
A big difference from ordinary road lighting is that tunnel lighting is more complex, and it is especially necessary to consider the adaptation of visual brightness changes when drivers enter and exit the tunnel. Since the human eye needs a certain process to adapt to the change of brightness, if the lighting effect is not ideal, it is easy to cause a "black hole" effect when driving into a tunnel, and it is easy to cause a "white hole" effect when driving out of the tunnel.
The purpose of tunnel lighting is to eliminate or reduce the black hole effect when driving into the tunnel, eliminate or reduce the white hole effect when driving out of the tunnel, transmit the necessary visual information to the driver, and prevent traffic accidents due to insufficient visual information. Vehicles driving inside provide a safe driving environment and increase driving comfort.
According to the design specification for highway tunnel ventilation and lighting, tunnels with a length greater than 100m should be equipped with lighting. Tunnel lighting can be divided into five sections according to the distance of driving in and out, namely approach section, entrance section, transition section, middle section, exit section. The lighting requirements of each section are different, which are explained as follows:
1. Approaching segment:
When first entering the tunnel, since the brightness outside the tunnel is much higher than that inside the tunnel during the day, if the tunnel is long enough, the driver sees a dark hole; if the tunnel is short, the driver will exit in front of the driver A "black box". After entering the tunnel, enter a dark tunnel from the bright exterior, the vision will have a certain adaptation time, and then the situation inside the tunnel can be seen clearly, so the visual problem of the vehicle in the approaching section should be solved at the entrance.
In the approaching section, light reduction measures such as shading awnings and awnings can be used to reduce the brightness difference inside and outside the tunnel during the day, while the guiding street lights set in the approaching section can be used at night to allow drivers to understand and adapt to the tunnel opening conditions.
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2. Entrance section
The entrance section is the first section of the four sections in the tunnel. During the day, the driver is in a "light and dark" adaptation process at the entrance section. It is necessary to strengthen the lighting to eliminate the "black hole" phenomenon. The road conditions at the entrance can be seen; the driver at the entrance at night is a "dark and bright" adaptation process, and it is necessary to appropriately reduce the brightness of the tunnel entrance to ensure the safety and comfort of the driver and the lighting economy.
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3. Transition section
In the daytime, when the driver drives from the entrance section to the middle section, in order to reduce the visual difference, it is necessary to set up the excessive lighting section, so as to meet the safety, comfort and lighting economy requirements of the driver's visual cognition. As the name implies, the brightness of the transition section should be gradually decreased. , the degree of decline, that is, the difference between the first few and the latter stage should not be greater than 3:1; at night, when the brightness difference between the entrance section and the middle section is not large, the brightness of the transition section and the nighttime brightness of the entrance section should be kept at the same level on the level.
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4. The middle section
The middle section is the area in the tunnel away from the influence of external natural light, and the driver's vision is only affected by the lighting in the tunnel. In order to meet the safety, comfort and lighting economy requirements of the driver's visual perception, it is necessary to keep the brightness in the tunnel at a reasonable and uniform level. Because no change is required, this segment only needs to provide the appropriate brightness level, which is determined by traffic flow and vehicle speed per hour.
However, the waste emitted by cars in the tunnel could not be dissipated in time, forming white smoke ahead, which was diffused by the lights into a light curtain, reducing visibility. Therefore, the lighting level is required to be higher than that of ordinary roads. At this low level, it is not possible to use a continuous strip of light, so it must be used to prevent interfering stroboscopic.
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5. Exit section
The exit section is an adaptation transition section for the driver to drive out of the tunnel from the tunnel. It should be noted that the adaptation is in "dark light" during the day and "light and dark" adaptation at night. At the exit of the tunnel during the day, the light at the exit is very bright, which will cause strong glare to the driver, so that the road conditions cannot be seen clearly, and traffic accidents are likely to occur. Therefore, during the day, the illumination of the exit section should be gradually strengthened to eliminate the white hole effect, so that the driver can adapt to the exit in advance. brightness.
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