When people have the need to travel at night, there is public lighting. Modern public lighting began with the emergence of incandescent light. Public lighting develops with the development of the times, the progress of science and technology and the continuous improvement of people's living standards. From people only require lighting the road surface to detect the situation of the road, to help people identify whether the road is a pedestrian or an obstacle, to help motor vehicle and non-motor vehicle drivers identify the characteristics of pedestrians, etc.The fundamental purpose of public lighting is to provide drivers and pedestrians with good visual conditions and guide them to travel, so as to improve traffic efficiency, reduce traffic accidents and crimes at night, and at the same time help pedestrians to see clearly the surrounding environment and identify directions. With the development of social economy and the continuous improvement of people's living standards, more and more people go to outdoor recreation, shopping, sightseeing, and other activities at night. Good public lighting also plays a role in enriching life, prospering economy and enhancing the image of the city.According to the view of public lighting, roads can be divided into four categories: special roads for automobiles, general streets, commercial streets, and sidewalks. Generally speaking, public lighting refers to special public lighting for automobiles. Among many purposes of public lighting, providing safe and comfortable visual conditions for motor vehicle drivers is the first.The public lighting source was a street light at the earliest, and then came high-pressure mercury light, high-pressure sodium (HPS) light, metal halide light, high-efficiency energy-saving light, electrodeless light, LED light, etc. Among the more mature street light sources, HPS lights have the highest luminous efficiency, generally reaching 100~120lm/W, and high-pressure sodium lights account for more than 60% of the total public lighting market in China (with about 15 million lights). In some communities and rural roads, CFL is the main lighting source, accounting for about 20% of the public lighting market. Traditional incandescent lamps and high-pressure mercury lamps are being phased out.