Dobbins JLUS IMP Public Draft Light Pollution Study

4. Mitigation Analysis Backlight Backlight is illumination that occurs behind the luminaire which is caused by the source of the light either by how it is manufactured or positioned as shown on the right. Light is reflected backwards, which can cause wasteful light to be emitted and produce glare and light pollution. It is recommended that the lowest possible backlight rating be used and not exceed a backlight rating of 3 (B3) for heavily used commercial areas, (B2) for all other nonresidential areas and (B1) for residential areas. Uplight Uplight is illumination that occurs above the 90‐degree angle of the luminaire, which can cause an inordinate amount of light to be emitted upwards causing glare and light pollution as shown on the right. It is recommended that the lowest possible uplight rating be used and not exceed an uplight rating of 0 (U0) for area and parking lot lighting. A maximum uplight rating of 2 (U2) may be used for low output, decorative pedestrian luminaires. March 2018 Glare Glare a visual sensation caused by excessive and uncontrolled brightness. It is recommended that the lowest possible glare rating be used and not exceed a glare rating of 2 (G2) for heavily used nighttime commercial areas, G2 for all other non‐residential areas, and G1 for residential areas. Color Temperature It is recommended that the color temperature of LED light sources not exceed 4100K. The bluer LED color temperatures (5000K and above) have a higher likelihood of perceived glare from the higher color temperature white light sources. In other words, glare is perceived to be produced from LEDs with color temperatures that are and exceed 5000K, e.g. some vehicle lights have been installed with these bluer LED light fixtures. Controls As intelligent control systems are becoming more prevalent in outdoor lighting systems, it should be expected that controls will be integrated into the majority of outdoor luminaires. Controls will allow the light output to be reduced during periods of low pedestrian and vehicular activity. It is recommended that luminaires are equipped with dimmable control gear and are capable of accepting a dimming control module from an intelligent control system. It is recommended that the Cobb County and the cities of Marietta and Smyrna establish a mechanism to inform private property owners of the above recommendations when they are retrofitting less than 50 percent of the lighting value. Potential avenues include utility incentives and replacement programs. DRAFT Dobbins Air Reserve Base Light Pollution Study Page 4‐5

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