With the rapid development of urban economic construction and transportation, the scale and quantity of lighting for urban construction is increasing, and the electricity consumption of urban lighting is also rising rapidly. How to achieve scientific and reasonable power saving has become an important issue under the premise of meeting urban road lighting requirements, achieving traffic safety and smooth traffic .
At present, the research on road lighting energy-saving methods at home and abroad is mainly reflected in the following two aspects: First, the use of high-quality and efficient new light source to replace traditional light sources, such as the â€œTen Cities and Ten Thousand Planâ€ launched by the Ministry of Science and Technology in 2009 is to make full use of The huge energy-saving potential of LED light sources is gradually replacing traditional light sources such as high-pressure sodium lamps, that is, focusing on the design of LED light sources and lamps [2-4]; on the other hand, on-demand illumination according to the requirements of road lighting in different time periods, such as early After midnight, half of the light source is turned off to achieve power saving effect . Recently, intelligent dimming technology and Internet of Things technology are used to realize automatic control of light source intensity in different periods to achieve energy saving [6-7]. Both of these methods are road lighting energy-saving design from the level of engineering implementation, ie tactical level. The premise must meet the existing road lighting design standards, which means that road lighting design standards have a crucial impact on lighting energy efficiency. . If the standard requirements are too high to affect the level of energy conservation, if the standard requirements are too low, it will affect driving safety. Therefore, starting from the road lighting design standards, it is necessary to study how to make the standard itself more conducive to energy saving under the premise of ensuring road lighting safety. It has a deeper significance in the research of road lighting energy saving. This research work can carry out road lighting. Energy-saving research has risen from a tactical level to a strategic level, enabling greater energy savings.
The formulation and research of national road lighting design standards by countries generally refer to international road lighting design standards based on the actual situation of existing road traffic. At present, there are two major standards systems in the world. The first is the International Commission on Illumination (CIE), "Road Lighting Recommendations for Motor Vehicles and Pedestrian Traffic" (115-1995), which is the vast majority of countries in the world. Adopted; the second is the Road Lighting (RP-8-00) [8-9] proposed by the Illuminating Engineering Society of North America (IESNA), which is mainly used in the Americas. Both sets of standards are comprehensively balanced between the two aspects of road safety and energy saving, and have been promoted on a considerable scale, but for the similarities and differences between the two sets of standards, the international only Some qualitative comparisons [10~12], as for the main differences between the two types of standards in evaluation methods, lighting indicators, energy-saving effects, etc., there is still no quantitative in-depth study. Therefore, an in-depth analysis of the quantitative differences between the two standards in the evaluation indicators and calculation methods and the related lighting effects and energy consumption differences, has a greater engineering guiding significance for promoting energy conservation and emission reduction from the strategic level of road lighting standards. And scientific value.
2 Comparison of two road lighting design standards
2.1 Recommended road lighting recommendations by the International Commission on Illumination (CIE)
In CIE115, motor vehicle roads are divided into five categories, M1~M5, and the road illumination quality is evaluated by the average brightness Lave, the total brightness uniformity Uo, the brightness longitudinal uniformity UL, the environmental ratio SR, and the threshold increment TI for evaluating glare. The evaluation contents and indicators are shown in Table 1 [8, 13~15].
Table 1 CIE Road Lighting Design Standards (115-1995)
2.2 Road lighting design standards proposed by the North American Lighting Engineering Association (IESNA)
In the American road lighting design standards, roads are divided into six categories according to road complexity and traffic volume. For each type of road, the high, medium and low grades are set according to the different materials of the road surface and the size of the traffic. Evaluation index specified value. IESNA has proposed three types of road lighting evaluation indicators, designers can choose the appropriate indicators to design according to needs. The three types of indicators are illuminance indicators (including average illuminance and illuminance uniformity), brightness indicators (including average brightness, brightness uniformity, and brightness longitudinal uniformity) and small target visibility indicators. Among them, the illuminance index and the brightness index all contain the brightness ratio index of the light curtain for evaluating glare, and the specific contents and indicators are shown in Table 2 .
2.3 Comparison of road lighting design standards
2.3.1 Qualitative comparison
According to the CIE and IESNA two types of road lighting design standards, the difference between the two types of standard motorway lighting design standards can be found in the following three points:
The first is the selection of evaluation indicators. The CIE mainly uses the brightness index to evaluate, including the threshold increment TI and the environmental ratio SR index. The IESNA uses three indicators, namely the illumination index, the brightness index and the small target visibility index STV, among which the illumination index and the brightness index are used. The light curtain brightness ratio indicator is included to evaluate glare.
Table 2 US Urban Lighting Design Standards (Importance and Brightness Recommendations)
Note: The US standard is not fully quoted, see the original standard 
The second is the calculation method of the evaluation indicators. The main difference is reflected in the calculation of the brightness index. CIE stipulates that there is only one observer in each lane and is fixed at 60 meters behind the starting position of the calculation area to observe the brightness of all matrix points in one lamp cycle (as shown in Figure 1). IESNA specifies that each row of the matrix in the calculation area has an observer, and each observer always observes the brightness of the matrix point 83 meters ahead of the direction of the matrix (as shown in Figure 2), meaning IESNA The observer in the standard performs lateral movement not only in the direction perpendicular to the lane but also in the direction of the parallel lane.
Figure 1 CIE road lighting calculation method diagram
Figure 2 IESNA road lighting calculation method icon
The third is the definition of the evaluation indicators and the specified values â€‹â€‹of the indicators. For average brightness Lave, total brightness uniformity Uo, and brightness longitudinal uniformity UL, CIE and IESNA are exactly reciprocal in their definition, and numerically, the CIE standard specified by the same indicator is significantly higher than the IESNA standard, just as As shown in Table 1 and Table 2, it can be seen from the table that the average brightness Lave of IESNA is 60% of CIE, and the brightness uniformity Uo is 82% of CIE requirement.
2.3.2 Quantitative comparison
In order to quantitatively analyze the difference in brightness calculation between the two types of standards, five typical road lighting fixtures of PHILIPS (the distribution of light distribution and optical parameters are shown in Figure 3) were selected for four lanes with different widths. The combination of 20 lamps and roads (shown in Figure 4 and Table 3) of the three lamp installation methods is calculated, and the difference between the brightness index values â€‹â€‹of the CIE standard method and the IESNA standard method under each combination is obtained (as shown in Fig. 5). Show). In Figure 5, the abscissa represents 20 combinations of different luminaires and lane widths. The ordinate represents the average luminance Lave, the total luminance uniformity Uo, and the luminance longitudinal uniformity UL obtained by the luminance calculation methods defined by CIE and IESNA, respectively. The relative value of the difference. It can be seen from the figure that the average brightness Lave and the brightness longitudinal uniformity value UL have little difference with the two standard calculation methods. The longitudinal uniformity UL of the brightness obtained by the IESNA calculation method is substantially smaller than the value obtained by the CIE method. Large, and the total brightness uniformity value Uo is significantly larger than the value obtained by the CIE calculation method. This means that the IESNA standard approach to designing luminaire layouts is easier to meet the standard requirements at lower energy consumption than the CIE standard approach.
Figure 3 Five types of lamps
Figure 4 Three ways of lighting
Table 3: Combination of luminaires and road types
Figure 5 Differences in brightness index values â€‹â€‹between two types of standards