Mitigating urban light pollution: A review of municipal regulations and implications for planners

Abstract

ABSTRACTPropelled by more energy-efficient technologies such as light-emitting diodes, the growth of outdoor light at night is raising concerns about light pollution (LP). Given mounting evidence of LP’s risks to human wellbeing, nature and wildlife, and views of the dark sky, this paper examines the extent to which LP concerns are addressed in land use plans, policies, and regulations in nine U.S. cities, including Flagstaff, Arizona, a city known for its model lighting code. Through a review of zoning and other ordinances, area and sectoral plans and policies, media reports, and interviews with planners, this study documents that LP has yet to be taken seriously in municipal codes of most study cities. Drawing from the Flagstaff model, it offers recommendations for evidence-based, objective standards for three key dimensions of LP-mitigation: limiting total illumination or lumens per acre, shielding of lamps, and specifying luminaire characteristics.ABBREVIATIONS AMA: American Medical Association; APA: American Planning Association; CCT: Correlated Color Temperature; CRI: Color Rendition Index; ESCO: Energy Service Companies; f.c.: foot candle; HPS: High-Pressure Sodium; IDA: International Dark-Sky Association; LED: Light-Emitting Diode; LP: Light Pollution; LPS: Low-Pressure Sodium; LZ: Lighting Zone; NSA: Narrow-Spectrum AmberKEYWORDS: Light pollutionurban planningsustainability AcknowledgmentsAn earlier version of this paper was presented at the 2021 Annual Conference of the Association of Collegiate Schools of Planning. I am grateful to Matthew Glaab for his research assistance, respondents from study cities who shared information and opinions about their local contexts, and three anonymous reviewers of an earlier version of this paper for their thoughtful notes and suggestions. All remaining errors and omissions, of course, are mine alone.Disclosure statementNo potential conflict of interest was reported by the author(s).Notes1. This is a unit of luminance, measured in candelas per square meter, in which the natural night sky measures at 1 mcd/m2 (or 1 millicandela per sq. meter) and the night sky lit with the full moon at 1.4 mcd/m2 (Source: en.wikipedia.org/wiki/Orders_of_magnitude_(luminance)). In comparison to lumens, which refer to the total amount of light emitted by a lighting apparatus, candela refers to the amount of light emitted by a lighting device in a particular direction. A light sphere that uniformly radiates one candela in all directions has a total luminous flux of 1 cd × 4π sr = 4π cd⋅sr or approximately 12.57 lumens (sr = steradian).2. Correlated-color (CCT) temperature is used to describe the light appearance provided by a light bulb. It is measured in degrees of Kelvin (K) on a scale from 1,000 to 10,000. Kelvin temperatures for commercial and residential lighting applications range from 2000 K to 6500 K, with the latter level of CCT typically associated with daylight. CCT is commonly used as a short hand to suggest the amount of blue light; however, this can be misleading. To produce the same amount of light, a 2300 K source could emit more blue than one with 3000 K (Schulte-Römer et al., Citation2018, p. 59).3. For example, New York requires lamp CCT to be between 3000 K and 4100 K, with minimum color rendering index of 65. A color rendering index (CRI) is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with an ideal or natural light source. Light sources with a high CRI are used in medical and artistic applications, where color is critical. Fluorescent lights range from about 50 to about 98. Typical LEDs have a CRI of 80 or more. (Source: https://en.wikipedia.org/wiki/Color_rendering_index).4. I am grateful to Dr. Christian Luginbuhl, astronomer, who patiently explained many aspects of outdoor lighting, developing objective codes to control for specific aspects, and his group’s experience developing many iterations of the Lighting Code in Flagstaff.5. This term was found in codes with capitalization, i.e., NITS (Omaha), as well as without (Seattle). Interchangeable with candelas per sq. meter, a unit of luminance, or light emitted per unit area, it is frequently used to specify the brightness of a display device, such as a billboard with dynamic images. Illinois Coalition for Responsible Outdoor Lighting (Citationn.d.) recommends a maximum limit of 5,000 NITS during the daytime. It contends that a limit of 150 NITS surface brightness for digital signs is comparable to the nighttime signage that is widespread across the nation and is aligned with the recommendations of the Illuminating Engineering Society of North America. It accepts a higher limit of 200 NITS for a sign under certain conditions, a level that is lower than Omaha’s (and Seattle’s and Houston’s) allowable maximum limit for such signs. Meanwhile, IDA’s (Citation2018) standards for illuminated signs for its Certified Dark Sky Community designation states, “Luminance levels between sunset and sunrise not to exceed 100 NITS (100 candelas per sq. meter) as measured under conditions of a full white display.”6. Light-affirmative rationales such as navigation, safety, and aesthetics are not included here; neither, given its near-ubiquity as well as near-irrelevance for reducing ambient light output or sky-glow, is energy-efficiency.7. Semi-cutoff standard is defined as “not more than five percent of peak foot candle intensity radiating above 90 degrees and 20% of peak intensity above 80 degrees.”8. These are specified by the American National Standards Institute and the Illumination Engineers Society for roadway and parking lot lighting. The standards offer lighting design criteria to help lighting engineers consider the following goals: Improve motorist visual quality; Provide quality light and increased contrast for seeing hazards; Illuminate conflict areas; Minimize environmental impacts of light at night; Employ lighting systems that are easily maintained and minimize energy use. Read more at ANSI/IES RP-8-21: Design Of Roadway Facility Lighting, https://blog.ansi.org/?p=160622.9. The program contains activities related to bird safety as it relates to nesting on poles, perching on wires, and tree and vegetation management.Additional informationNotes on contributorsKameshwari PothukuchiKameshwari Pothukuchi is distinguished service professor of urban studies and planning at Wayne State University. Her research interests include planning for community food systems, equitable community development, and nature-friendly cities.