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4 Introduction The overarching goal of the survey was 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- and construction- related modifications currently used by state transportation agencies and authorities. Survey Methods The survey was designed to increase understanding of 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 gain information about the following areas: ⢠State of adoption, construction, and maintenance of LED roadway lighting and ⢠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 collected in September 2017 for all of the questions are presented in Appendix A and 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 were currently using LEDs. Approximately 7% of those who responded had no LED roadway light- ing installed. About 68% of the respondents reported that all new roadway lighting installations used LED lighting, while 15% reported that new lighting installations did 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 were currently in design, construction, or installed and fully operational. Approximately 43% of all the LED roadway lighting used a CCT of 4000K. A small number of the respondents reported the use of 3000K (12%) or 5000K (14%) CCTs; the rest of the respondents reported the use of a combina- tion 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. C H A P T E R 2 Current State of the Adoption of and Guidance for Solid-State Lighting
Current State of the Adoption of and Guidance for Solid-State Lighting 5 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 reported using some sort of adap- tive lighting control system for reduced illumination. Similarly, about 93% of the respondents said they do not use any kind of design modifications, such as occupancy sensors or color tuning, with LED roadway lighting. Design Guidelines and Criteria for LED Roadway Lighting More than half (68%) of the respondents said they did not have a design manual or standard specifically for LED roadway lighting. However, 63% reported having specific technical specifi- cations for construction of LED roadway lighting. More than 80% of the respondents used either ANSI/IES RP-8-18 (IES 2018) (40%) or the AASHTO Roadway Lighting Design Guide (48%) for roadway lighting guidelines. Approximately 11% of respondents used roadway lighting guide- lines that were developed in-house. A majority (70%) of respondents said 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 (â¼82%) reported that lighting calculations for roadway lighting designs are required to be reviewed. Approximately 15% of the respondents reported that lighting cal- culations are reviewed on the basis of 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; about 31% reported that they sometimes require verification. Conclusion On the basis of the results of the survey, the following conclusions can be drawn: ⢠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. ⢠A majority of LED roadway lighting uses 4000K CCT luminaires. ⢠Adaptive lighting technologies and other design modifications that support reduced illumina- tion are not widely used at present. ⢠While the majority of the respondents do not have LED-specific guidelines for roadway light- ing design, they are willing to use them if guidelines become available. In the absence of such guidelines, DOTs are using either ANSI/IES RP-8-18 or the AASHTO Roadway Lighting Design Guide for guidance on roadway lighting. ⢠Although a majority of the state DOTs require lighting calculations as part of the design review, very few verify lighting levels after construction.
