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5 CHAPTER 2. CURRENT STATE OF SSL ADOPTION AND GUIDANCE INTRODUCTION The overarching goal of the survey is to understand how SSL has been adopted in roadway lighting applications. More specifically, the survey provides information on the use of LEDs for roadway lighting, implementation of adaptive lighting strategies, and design/construction-related modifications currently used by state transportation agencies and authorities. SURVEY METHODS The survey was designed to understand how SSL has been adopted for roadway lighting and the design criteria and management associated with it. The survey has a list of 13 multiple-choice questions and was developed to understand the following areas: â¢ State of adoption, construction, and maintenance of LED roadway lighting â¢ Design guidelines, criteria, and review for LED roadway lighting SURVEY RESULTS The survey was distributed to 49 respondents from several state DOTs in the United States. The survey response rate was 61%. The results for all of the questions collected in September 2017 are in Appendix A. Survey results are summarized below. State of Adoption, Construction, and Maintenance of LED Roadway Lighting Eleven percent of the respondents reported that 25% of their roadway lighting systems are currently using LEDs. Approximately 7% of those who responded do not have any LED roadway lighting installed. About 68% of the respondents reported that all new roadway lighting installations use LED lighting, while 15% of respondents reported that new lighting installations do not use LEDs. A small percentage of respondents reported the use of HPS lighting for new installations. A significant majority of respondents (> 90%) reported that LED roadway lighting projects are currently in design, construction, or installed and fully operational. Approximately 43% of all the LED roadway lighting use a CCT of 4000K. A small number of the respondents use 3000K (12%) or 5000K (14%) CCTs; the rest of the respondents use a combination of CCTs. A majority of the respondents (63%) reported that during spot replacement, luminaires are replaced with similar luminaires. About 22% of the respondents reported that they allow for mixed sources when luminaires fail. A majority of the respondents (88.5%) reported that they do not use adaptive lighting control systems for LED roadway lighting. Only 11.5% of respondents use some sort of adaptive lighting control system for reduced illumination. Similarly, about 93% of the respondents do not use any kind of design modifications like occupancy sensors or color tuning when using LED roadway lighting.
6 Design Guidelines and Criteria for LED Roadway Lighting More than half (68%) of the respondents do not have a design manual or standard specifically for LED roadway lighting. However, 63% of the respondents have specific construction technical specifications for LED roadway lighting. More than 80% of the respondents use either ANSI/IES RP-8 (40%) or the AASHTO Roadway Lighting Design Guide (48%) for roadway lighting guidelines. Approximately 11% of respondents use roadway lighting guidelines that were developed in-house. A majority (70%) of respondents reported that if a national design and technical specification manual were available specifically for LED roadway lighting, they would use it. None of the respondents said they would not use it. Most respondents (~82%) reported that lighting calculations for roadway lighting designs are required to be reviewed. Approximately 15% of the respondents reported that lighting calculations are reviewed based on the size of the project. However, only 23% of respondents indicated that lighting levels need to be verified after construction and prior to acceptance. Forty-six percent of the respondents reported that they do not require verification of light levels after construction, and about 31% sometimes require verification. CONCLUSION Based on the results of the survey, the following conclusions can be drawn: â¢ Even though LED roadway lighting systems are not currently widely installed, their adoption is growing rapidly; almost all new roadway lighting construction will use LEDs. â¢ A majority of LED roadway lighting use 4000K CCT luminaires. â¢ Adaptive lighting technologies and other design modifications that support reduced illumination are not widely used at present. â¢ While the majority of the respondents do not have LED-specific roadway lighting design guidelines, they are willing use them if guidelines were available. In the absence of such guidelines, DOTs are using either ANSI/IES RP-8 or the AASHTO Roadway Lighting Design Guide for guidance on roadway lighting. â¢ Although a majority of the DOTs require lighting calculations as part of the design review, very few verify lighting levels after construction.