Solid-State Roadway Lighting Design Guide: Volume 1: Guidance (2020) / Chapter Skim
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Chapter 3 - Techniques of Lighting Design
Chapter 3 - Techniques of Lighting Design
Pages 17-28
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From page 17... ...
It offers pole placement guidance, calculation methods, and a warranting system to assist in the prioritization of lighting systems for various roadway types and operating conditions. Application of SSL does not significantly change any of the requirements for lighting design techniques in the current AASHTO guide, but installations may benefit from additions to the current requirements and recommendations.
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Source Color Selection SSL products offer a range of colors of varying spectral content that can be applied to a roadway, as shown in Figure 14. Each of these spectral content sources has properties that can affect subjective preference, visibility of objects, and light scatter and physiological influences, which are further discussed in Chapter 11.
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. The results indicate that there is a spectral component to detecting objects, and certain CCT LED sources (using current conventional technology of blue LED with yellow phosphor coatings)
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. Figure 13. Classification method for highways (H class = 5 weighting factors)
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. Newer LED optical systems offer very controlled light distribution, so areas adjacent to the roadway, including bike lanes and sidewalks, may not receive adequate lighting if traditional design methods are used with LEDs.
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. Research for this project shows the Research performed for NCHRP 05-22 shows that detection distances advantage to providing lighting outside are increased when lighting is used in areas adjacent to the roadway.
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Warranting Considerations The AASHTO Roadway Lighting Design Guide establishes warranting conditions for highways and freeways; it does not, however, establish warrants for streets and other types of roadway facilities. Although it must be noted that many roadway improvements provide additional safety benefits to users and that warrants do not establish a requirement to light a roadway, but merely assist in prioritizing projects and funding of those roadway improvements, other resources are available for use in light versus not-light evaluations.
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. CMFs roadways, crash modification factors represent the change expected in crash frequency from a specific change or other warranting methodologies in conditions.
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Techniques of Lighting Design 25 Source: TAC (2006)
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Where the roadway classification or roadway land use classification changes, a separate warrant analysis should be conducted for each roadway section. A single warrant analysis may be used where classifications are relatively constant along the segment of roadway under consideration.
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Perceived glare is something generally sensed by abutters to the high-mast installation and difficult to quantify. Even if the light trespass illuminance levels are well below recommended limits, the inherent brightness of some LED sources against a dark sky or background can cause complaints from some residents abutting the roadway.
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From page 28... ...
• Consider high-mast lighting only for large area lighting or very wide roadway cross sections, as it can create more light trespass and perceived brightness issues for abutters. • Identify sensitive receptors and housing areas close to the roadway right-of-way early in the design process.
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