Light Nuisances - Ambient Light, Light Pollution, Glare
This page provides information related to light pollution and nuisances for local governments in Washington State, including examples of local code provisions.
It is part of MRSC's series on Nuisances: Regulation and Abatement.
Light pollution includes misdirected light, stray light, avoidable reflected light, light during hours when it is not needed, and light levels in excess of what is necessary for the task.
According to the Illuminating Engineering Society of America, light trespass complaints can usually be classified into two categories: unwanted light illuminating an area or property and excessive brightness in the normal field of vision. Problems of glare from building reflections are generally regulated through building and zoning codes.
For new development, the State Environmental Policy Act (SEPA) Checklist (WAC 197-11-960) at Environmental Element (11) covers light and glare and includes questions. However, beginning in 2022, residential, multifamily, or mixed-use developments in a city or town planning under the Growth Management Act are exempt from SEPA appeals on the basis of light or glare, as long as the project is subject to locally adopted design review requirements. See RCW 43.21C.501(3)(b).
The International Dark-Sky Association and the Illuminating Engineering Society of North America partnered to create the Model Lighting Ordinance (MLO), which is designed to help municipalities develop outdoor lighting standards that reduce glare, light trespass, and skyglow. The MLO offers several innovations to outdoor lighting regulation, including the use of five lighting zones to classify land use with appropriate lighting levels for each. Zones range from LZ0, designed for pristine natural environments and limited outdoor lighting, to LZ4, for limited application in areas of extensive development in the largest cities.
Examples of state-based ordinances related to outdoor lighting standards are as follows:
- Bainbridge Island Municipal Code Sec.18.15.040 — Provides regulations that preserve and enhance the view of the dark sky; promote health, safety, security, and productivity; and help protect natural resources.
- Bothell Municipal Code
- Chelan Municipal Code Ch. 17.62 — Provide standards for appropriate evening lighting practices and systems that will enable people to see essential detail, facilitate safety and security, and curtail the degradation of the nighttime visual environment; Includes many graphics on approved lighting designs.
- Enumclaw Municipal Code Sec. 19.22.020 — Includes provisions on Arc welding, acetylene torch-cutting or similar processes under industrial and exterior lighting performance standards.
- Goldendale Municipal Code Ch. 15.52 — Purpose is to prevent excessive illumination, glare, and reflection in areas adjacent to astronomical research facilities, such as observatories, where such light intrusion would hinder use of sensitive optical devices. Includes images of approved outdoor lighting designed to ensure no light is emitted, refracted, or reflected at or above a horizontal plane running through the lowest point on the fixture.
- Island County Code Sec. 17.03.180(R) — Provides outdoor lighting standards to ensure compatibility with neighboring uses while preserving the overall rural character of the county.
- Kennewick Municipal Code Ch. 18.39 — Establishes regulations limiting the area that certain kinds of outdoor lighting fixtures can illuminate.
- Lakewood Municipal Code Sec. 18A.60.095 — Divides the city into three lighting zones, including coverage of Joint Base Lewis McChord, with recommendations for each zone depending on intensity and purpose of land use.
- Lynnwood Municipal Code Sec. 17.05.110 — Declares a nuisance any activity that produces enough light or glare beyond the parcel within which the use is located, including outdoor lighting, signage, sources of artificial illumination, and building materials with high light reflective qualities.
- Mountlake Terrace Municipal Code Sec. 19.120.030 — Addresses uses producing artificial light, utilizing light for night operation, or causing glare.
- Oak Harbor Municipal Code Sec. 20.14.060 — Outlines policy and policy intent to reduce light and glare.
- Pasco Municipal Code Ch. 12.32 — Defines "outdoor lighting fixtures" as lighting for billboards, street lights, shopping center or parking area lights, externally or internally illuminated on-site or business advertising signs, and yard type lighting; Covers shielding, unlawful acts temporary exemptions, exclusions, enforcement, and penalties for violation.
- Seattle Parks and Recreation Design Standard 25 56 00 (2011) — Provides criteria for selection, design, and placement of lighting fixtures in parks and other parks facilities.
- Tumwater Municipal Code Sec. 18.40.035 — Requires lights be fully shielded and not result in light shining on other properties, in the sky, on the roads, or anywhere else off of source. Includes a list of exceptions.
- International Dark Sky Association
- Criteria for Community-Friendly Outdoor Sports Lighting (2018) — Offers criteria to minimize obtrusive light spill and glare into surrounding neighborhoods and natural areas, meets sustainability and climate-friendly goals, and reduces sky glow to the greatest extent practicable.
- Outdoor Lighting Code Handbook, Sec. 5.02: Sports Lighting (2002) — Offers recommendations on lighting for nighttime sports.
- Seattle Parks and Recreation: Design Standards for Athletic Field Lighting (2011)
- Illuminating Engineering Society of North America — Publishes standards for lighting, including sports and recreational lighting, parking lot lighting, and roadway lighting.
- International Dark-Sky Association — Builds awareness of the impact of light pollution, and educates businesses, policymakers, and the public on the value and effectiveness of quality nighttime lighting, including regulations and best practices. Publishes the Outdoor Lighting Code Handbook (2002).
- Methow Dark Sky Coalition — A nonprofits that advocates and educates on the importance of reducing light pollution in the Methow Valley.