What are the three important parameters of road lighting?
Road lighting, the installation of luminaries on roads to provide necessary visibility to vehicles and pedestrians at night. Road lighting can improve traffic conditions, reduce driver fatigue, and is conducive to improving road capacity and ensure traffic safety, in addition, but also beautify the city appearance, is an indispensable public facilities in urban construction. Street, road, street square, bridge and tunnel lighting are road lighting, some countries also include free parks and urban green space public lighting.
- The types of road lighting can be divided into three types: continuous lighting, special area lighting and buffer lighting.
- First of all, road lighting should meet the requirements of drivers in the night driving can accurately identify the various conditions on the road, respond to obstacles in time, avoid traffic accidents, and reduce the visual fatigue of drivers.
- Although the human eye has a wide field of vision, the shape, color and brightness difference of the target can be clearly identified only when the target is in the central field of vision, that is, the Angle of view of 1 ~ 2° near the center of vision. Therefore, it is suggested by the International Lighting Committee that: it can be considered that the average viewpoint height of the driver when driving is 1.5 meters, the front center field of vision is 1°, and the staring distance is 60 ~ 160 meters straight ahead. The road brightness and light distribution within this range have a direct effect on the driver’s vision.
- In 1977, the International Lighting Commission issued the recommended standards for road lighting, and proposed that average road brightness, road brightness uniformity and limited glare were taken as three technical indexes to evaluate road lighting.
- I. Average road brightness Since there needs to be a certain z-small brightness difference between the surface of the object and the road surface to detect the object, the average road brightness is an important indicator. According to the test, the average road brightness value should be 1.5 ~ 2.0 kdra per square meter.
- 2. Road brightness uniformity It is divided into whole road brightness uniformity and longitudinal brightness uniformity. The former represents the brightness uniformity that affects the driver’s comfort; The latter represents the brightness uniformity that affects the visibility of obstacles. International Commission on Lighting values see Table 2 international Commission on Lighting values for road lighting.
- 3. Limit glare There are two types of limited glare: disabling glare and uncomfortable glare. Disabling glare is physiological, which can hinder vision and reduce visibility, but does not necessarily cause uncomfortable feelings. The increase rate of threshold brightness of typical visual work targets of common drivers is expressed by TI. The smaller the TI(%) value is, the smaller the incapacitated glare is. The International Commission on Lighting stipulates that TI should be less than or equal to 10%. Uncomfortable glare is psychological and makes people feel uncomfortable, but does not necessarily interfere with vision. When driving, glare caused by lighting facilities reduces the degree of driver comfort, which is commonly expressed as glare control level G. The larger the G value is, the smaller the uncomfortable glare is. The International Commission on Lighting states that G should generally be greater than or equal to 6.
Facilities to choose
- According to the specific road and environment, the lighting device and installation mode should be reasonably selected to achieve good lighting effect and save energy. The lighting device should have a reasonable light distribution, so that it can be effectively targeted to the lighting object, limit glare, and protect the light source. In the past, incandescent lamps were mainly used as lighting sources. Now, high-efficiency gas discharge lamps, such as fluorescent high-pressure mercury lamp, high and low pressure sodium lamp and metal halide lamp, are used. The installation mode has suspension type, suspension cable type and multi-lamp combination type.