Solid-State Roadway Lighting Design Guide: Volume 2: Research Overview (2020)

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6 The project panel noted that the SSL Guide needs to be straightforward and concise, and that the document should include related reference materials and design methodologies. The panel also asked that the guide follow the structure of the AASHTO Roadway Lighting Design Guide (2018b) so that adoption of the results from this research can be easily applied to future revisions of that document. This chapter reviews the structure of the current AASHTO Roadway Lighting Design Guide and of the SSL Guide. AASHTO Roadway Lighting Design Guide The contents of the 2018 AASHTO Roadway Lighting Design Guide are as follows: Chapter 1: Introduction. Reviews the content of the guide, necessary expertise, and design considerations. Chapter 2: Master Lighting Plans. Outlines the purpose, benefits, and content for develop- ing a Master Lighting Plan. The section also discusses electrical and lighting management systems. Chapter 3: Techniques of Lighting Design. Discusses design metrics (illuminance, luminance, glare, uniformity, and contrast models); benefits of lighting, including warranting methods; lighting design values (roadways, sidewalks, and pedestrian and bicycle ways); and pole place- ment and roadside design considerations. Chapter 4: Tunnels and Underpasses. Discusses the purpose of tunnel lighting, warrants, and design considerations. Defaults to Illuminating Engineering Society (IES) and International Commission on Illumination (CIE) for detailed design approach. Chapter 5: Work Zone Lighting and Temporary Roadway Lighting. Provides a brief discus- sion of work zone lighting. Chapter 6: Roundabouts. Discusses warrants and design values for roundabouts. Chapter 7: Electrical System Requirements. Discusses some requirements for electrical systems. The current draft of the next edition includes some SSL-specific electrical and control items. Chapter 8: Safety Rest Areas. Discusses features, warrants, and design values for various loca- tions within a safety rest area. Chapter 9: Overhead Lighting. Includes various sign types, warrants, area classifications, sign lighting level and uniformity, and luminaire placement. Chapter 10: Maintenance Considerations in Roadway Lighting Design. Discusses fixture, support structure, and electrical system maintenance. Chapter 11: Sky Glow and Light Trespass. Discusses sky glow, light trespass, glare, and poten- tial means for mitigation. The current draft of the next edition also includes light trespass limits. C H A P T E R 3 Structure of the Solid-State Lighting Guide

Structure of the Solid-State Lighting Guide 7 Solid-State Lighting Guide Solid-State Roadway Lighting Design, Volume 1: Guidance (SSL Guide) follows the general structure of the AASHTO Roadway Lighting Design Guide. The content of the SSL Guide is based on the collected research and testing performed as part of this project. The guide uses dual English/SI units where applicable. The contents of the guide follows: Chapter 1: Introduction. Includes a general discussion of SSL lighting technology, SSL differ- ences compared to legacy HID sources, design differences when applying SSL technology, and SSL impacts to other highway systems. Chapter 2: Lighting Master Plan. Discusses differences that SSL lighting introduces to the master planning process. Key elements of this chapter include – Adaptive lighting control technologies, including types, system selection, general use, and the use of the adaptive lighting system as an asset management tool; – Differences in adaptive technologies ranging from luminaire output options to full control and monitoring systems as well as various communication and data methods and components; – Maintenance considerations in system planning; – The use of adaptive lighting systems on freeways versus streets and arterials; – Application of ornamental versus conventional lighting systems; – Approach differences for freeways and streets and arterials; – SSL appearance and acceptance in terms of discomfort glare, color preferences, and poten- tial methods for approaching and addressing these types of issues; and – Integration of SSL with Smart city and ITS systems. Chapter 3: Techniques of Lighting Design. Discusses the differences that SSL technology will introduce into the design process for roadways, streets, sidewalks, pedestrian ways, and bike- ways. This chapter includes classification, warranting, and differences in design approach to accommodate adaptive lighting. Where applicable, the structure of the chapter separates freeway design elements from street and arterial design elements. Key items investigated as part of this project include – Off-road lighting and whether it should be added as a design criterion for improved visibility, – Any new metric for roadway lighting design that the research demonstrates is ready for application and offers an improvement to the current AASHTO design methods of illu- minance and luminance, – Design criteria for disability and discomfort glare as it applies to SSL (the veiling lumi- nance ratio is currently included as the disability glare metric in the AASHTO Roadway Lighting Design Guide, and discomfort glare is not addressed), – Changes to the current design practice to accommodate SSL in terms of light level and methodology used, including visibility as well as driver behavior modification and whether they are applicable at this point of development, – Lighting levels for use with adaptive lighting systems and methodologies for their application, – Impact of weather and climate on lighting levels or adaptive lighting approach, – Retrofitting considerations for SSL, and – Warranting alternatives and discussion of safety reports using the Highway Safety Manual (AASHTO 2010) and crash modification factors. Chapter 4: Tunnels and Underpasses. Considers some basic differences between SSL and HID technology and reviews lighting controls for tunnel and underpass applications on the basis of current practice and existing research. Chapter 5: Work Zone Lighting and Temporary Roadway Lighting. Discusses applying SSL technology to the roadways in work zones and temporary roadway lighting and any differences

8 Solid-State Roadway Lighting Design caused by glare or optics. It also covers the approach and departure points from the work area and impacts to and visibility of areas adjacent to the work area. Chapter 6: Roundabouts, Interchanges, and Intersections. Discusses impacts of SSL as it applies to conflict points, pedestrian detection, and other considerations for roundabouts, intersections, and interchanges. Chapter 7: Electrical System Requirements. Discusses differences in the approach to electrical requirements for SSL. Key items included are – Voltage ranges for SSL, voltage drop requirements, and power factor considerations; – Electrical requirements for the application of adaptive lighting systems and asset management; – Voltage tolerances and surge suppression requirements; and – Potential control system requirements if color tuning or other control functions are used. Chapter 8: Safety Rest Areas. Discusses any modifications to parking areas, entrance and exit roads, and lighting control applicable to SSL systems. Chapter 9: Roadway Sign Lighting. Addresses modifications to sign lighting necessitated by SSL, including research results pertaining to the visibility of signs in various weather conditions, the use of different colors, and spectral content sources. Chapter 10: Operations and Maintenance Considerations. Discusses operation and mainte- nance (O&M) considerations for SSL. Key items addressed in this chapter include – Maintenance similarities and differences of SSL products, – Different methodologies used for determining light loss factors for SSL and resultant impacts, – Application of adaptive lighting systems in O&M, – Use of asset management systems as part of O&M, and – Cost–benefit analysis methods for determining the overall O&M costs of a lighting system as it relates to SSL technologies. Chapter 11: Potential Environmental Impacts. Discusses potential environmental and health impacts related to the implementation of SSL technologies. Specific items include – Role of adaptive lighting in addressing potential impacts, – Spectral content and impacts, – Limits for disability and discomfort glare, – Limits for light trespass and sky glow considerations, and – Balance of needs and exceptions based on specific area and safety conditions. – Methods for assessing the potential of SSL to cause circadian disruption and impacts on wildlife and plants as compared with HID, and – Nuisance glare and spectral properties. Annex A: Design Examples. Examples of lighting for a freeway and a street are included to mirror the chapters of the current AASHTO Roadway Lighting Design Guide (AASHTO 2018b) and additional recommendations included in this report and the SSL Guide. Annex B: Solid-State Lighting Sample Specifications. This specification includes SSL lumi- naires and controls and addresses conventional and ornamental roadway lighting, adaptive lighting control systems, tunnel and underpass lighting, high-mast lighting, and roadway sign lighting. There are separate specifications for roadways and tunnels.