Road lighting has an important impact on reducing the incidence of traffic accidents at night. Studies conducted in various countries over the past few years have shown that good road lighting can reduce night traffic accidents by about 30%. Road lighting power accounts for about 20% to 30% of total national lighting consumption. The choice of light source has a great impact on the safety and energy saving of road lighting.
The common light source for road lighting is high pressure sodium lamp (HPS), and a few use metal halide lamp (MH) or high pressure mercury lamp (HPM). Their relevant technical parameters are shown in Table 1.
Table 1 Comparison of typical MH, HPS and HPM light source specifications Source power / WZ life / h color rendering index Metal halide lamp (MH) High pressure sodium lamp (HPS) High pressure mercury lamp (HPM) problem is from the perspective of energy saving and safety Consider which light source is more suitable for road lighting. Generally speaking, the light source selection first considers the light efficiency of the light source. At present, the main basis for the selection of HPS lamps in road lighting is that it has a high luminous efficiency of about 120 lm*W-1. However, the light effect here is the data obtained under the condition of clear vision (> 3cd*m-2). As the brightness level decreases, the visual function of the human eye will have a Purkinje shift, if using the visual conditions. The light effect to evaluate the effect of the light source under the condition of road illumination (in the middle vision) will produce a certain error.
Recently, according to the characteristics of the human optic nerve, it has been suggested that when the illumination level and other conditions are the same in the peripheral detection, the MH lamp is more effective than the HPS lamp and passes the reaction time. The specific values ​​are shown in Table 2.
When the brightness level is lowered, the effective light efficiency of the HPS lamp is significantly reduced, while the effective light effect of the MH lamp is increased. If the nominal luminous efficacy of MH lamp, only 3 lamp and only lamp is 80, 116.7 and 52*, 1, when the brightness level is higher than 0.1<14-2, only 3 lamps have effective light effect. Although it has decreased, it is still higher than MH lamp; when the brightness level is lower than about 0.1cd*m-2, MH lamp has higher effective light efficiency; under dark vision conditions, the effective light effect of MH lamp is about Yes 2 times j from. It can be seen that the effect of net relative spectral energy distribution on light efficiency begins to show when the brightness is less, which is consistent with the definition of intermediate visual brightness range (0.0013 cd*m-2).
Table 2 MHHPS and HPM at different brightness levels and LEC 2 (Ming Vision)-5 (dark vision) 4 fields of view. The trend of the left side field of view and the right side field of view is consistent. However, since the data of the right side field of view has poor normal distribution, the reliability of the data is degraded. Therefore, only the left field of view data is taken for analysis. The left field of view value under MH lamp conditions is 2.0 degrees higher than that of the HPS lamp. That is, the MH lamp is more effective than the HPS lamp in peripheral detection corresponding to night road lighting conditions. The results of the variance analysis of the left field of view are shown in Table 4. The significance level P=0.054. The variance analysis results of the left side field of Table 4 show the square of the field of view and the degree of freedom of the mean square F-specificity within the left-view group between the P-value groups. A total of 5 discussions because the measurement of the field of view belongs to psychophysics.
The relationship between spectral light efficiency function, LEC value and visual function experiment LEC can provide the choice of light source for road lighting design, which is beneficial to the safety and energy saving of road lighting; in the study of visual function under intermediate visual brightness level, LEC can quantitatively describe the difference between different relative spectral energy distributions, which is helpful for in-depth quantitative analysis. Of course, the rigorous quantitative determination of LEC values ​​also requires the standardization of intermediate visual functions and further experimental proof.
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