How to choose tunnel lighting
General lighting in the tunnel
General lighting includes basic lighting necessary to ensure normal traffic in the tunnel and enhanced lighting to eliminate the effects of "white holes" and "black holes" at entrances and exits. The basic lighting arrangement scheme of the tunnel is: staggered arrangement of lights on both sides with an interval of 10m. The lamps are installed on the sidewall of the tunnel at a distance of 5.3m from the center of the road. For the sake of beauty, the installation height of the enhanced lighting fixtures is consistent with the basic lighting, and they are evenly arranged in the basic lighting fixtures.
According to the specification, general lighting is a first-class load. According to the requirements of the "Code for Electrical Design of Civil Buildings": "Especially important lighting loads should be automatically switched over at the last-stage switchboard of the load, or two dedicated circuits with about 50% of the lighting fixtures can also be used. Obviously, “the automatic switching of power supply at the last-stage switchboard of the load” is not suitable for tunnel lighting. This tunnel uses “a power distribution method with approximately 50% of the lighting fixtures each with two dedicated circuits”. In this way, even if there is a power supply or a transformer for maintenance or failure, at least half of the lamps in the tunnel can be guaranteed to light up normally, which will not cause the general lighting lamps of the entire tunnel to go out and cause danger to high-speed vehicles.
The lighting in the tunnel is controlled according to the brightness requirements and traffic volume of each section in different environments. The brightness monitors and loop coils installed inside and outside the tunnel are used to detect the light intensity near the tunnel entrance, and the traffic volume of the tunnel is used to control the lighting brightness of each section, so that the driver can adapt to the change of light intensity inside and outside the tunnel as soon as possible. Eliminate viewing angle obstacles caused by light intensity changes, so as to meet the brightness requirements of the tunnel, ensure driving safety, and extend the life of the lamps and save energy. According to the requirements of the “Code for Design of Ventilation and Lighting of Highway Tunnels”, “Entrance section shall be strengthened during the daytime with four levels of control: sunny, cloudy, and heavy shade; basic lighting shall be divided into two levels: heavy traffic and small traffic at night; Two-level control during day and night".
Most drivers generally turn on their lights when entering a tunnel, but some drivers turn off their lights after entering a tunnel with general lighting turned on. This is very dangerous. Although the general lighting we mentioned earlier is powered according to the primary load, the possibility of simultaneous failure of the two power sources cannot be ruled out. If the general lighting is cut off, the danger of driving at high speed in a narrow space such as a tunnel without turning on the lights is self-evident, and a series of traffic accidents such as rear-end collisions and collisions due to the driver's panic will occur. Tunnels equipped with emergency lighting can completely reduce the occurrence of such accidents. When general lighting is out of power, some emergency lighting fixtures continue to work. Although the brightness is lower than general lighting, it is enough for drivers to take a series of safe driving. Measures, such as turning on the car lights, slowing down, etc.