At present, traditional high-pressure gas discharge lig […]
At present, traditional high-pressure gas discharge light sources (HID), such as high-pressure sodium lamps (HPS) and metal halide lamps (MH), are still the main force of tunnel lighting. The tunnel lighting scheme requires a high minimum illuminance to provide a safe environment for users. The luminaire must be able to provide a high level of light at a considerable distance from the plane. The typical installation height of road tunnels is 5-7 meters, providing clearance for high-side vehicles.
High-pressure sodium lamps and metal halide lamps are very attractive to tunnel lighting scheme designers, providing both low unit cost and high illuminance. Arrays of high-pressure sodium lamps and metal halide lamps usually have a power of up to 400W per lamp to meet the illumination requirements.
However, the disadvantages of high-pressure sodium lamps (HPS) (Figure 1) and metal halide lamps (MH) are obvious. These two types of lamps consume a lot of energy, usually have low light quality, and cannot provide uniform lighting in the tunnel, and if a failure occurs, expensive maintenance programs are required to remedy. Now, with the advancement of LED technology, tunnel operators have a new choice, which is more and more attractive from the public and operational perspectives.
The most obvious advantage of LED-based tunnel lights is their long life and high efficiency:
In typical tunnel lighting applications, high-quality LED lighting systems can provide >100 lumens/watt. Since the LED is a directional point light source, its light output can be accurately transmitted to the required area, providing additional system efficiency compared with the HID system.
LED is a very reliable semiconductor device with a very long service life, which greatly reduces maintenance and service costs.