The principal purpose of most lighting codes is to limit adverse impacts arising from the production and use of outdoor lighting on the general (public) environment – that is, on the sky (sky glow), on other property (glare; light trespass), on the power grid (energy use and efficiency; carbon dioxide production), or on ecosystems (disturbance to animals, insects and plants). Some lighting codes focus instead or in addition on lighting “quality” on the property where the lighting is installed (illuminance, uniformity). The usual approach to regulating cross-boundary impacts is through zoning law; the approach to on–property “quality” is sometimes instead through building codes.
The legal basis for regulating the use of private property in the U.S. was originally based in the common law concept of “nuisance.” Under common law, it is recognized that persons are entitled to “use and enjoyment” of their lands. If one property owner uses their land in a way that interferes with the use and/or enjoyment of another, the affected party may be entitled to a legal claim of nuisance and mitigation of its cause. Zoning laws or codes extend and improve the nuisance concept by providing proactive notice that certain uses are prohibited or limited on the basis of the cross-boundary impacts. Lighting codes, when enacted as part of zoning (the most common practice), are thus generally not concerned with aspects of lighting design that do not directly relate to cross-boundary impacts (e.g. illumination levels on the property where the lighting is installed).
To address the cross-boundary impacts of lighting use, three principal aspects regarding the design of lighting hardware or systems are critical:
- Shielding of fixtures
- Spectrum of light sources
- Amount of light
Though all three factors are important, the relative importance in limiting adverse impacts is generally ranked as shown. Shielding: Research shows that full shielding can reduce sky glow by 50% to over 90% when compared to a typical mix of partially shielded and unshielded lighting1. As shielding dramatically reduces glare and light trespass as well, it is and should be the highest priority in lighting codes. Spectrum: Specification of yellow light sources (high-pressure sodium and PC-amber LED, or low-pressure sodium and AlInGaP “narrow-band” amber LED) for the majority of lighting uses can reduce sky glow by 70% to almost 90% when compared to white sources such as metal halide, fluorescent and LED2. Amount: Finally, reasonable limitations on the total lighting (lumen) amount reduce the frequency and degree of careless and/or competitive over-lighting. Lumen caps of 50,000 – 100,000 lumens per acre have been shown in a study in Flagstaff3 to reduce average lighting amounts (and thus all light pollution impacts) by 25% to 70% compared to average un-capped commercial lighting practice, and in particular applications such as service station canopy lighting by 90% or more.
1. Luginbuhl, C.B., et al., 2009, Lighting and Astronomy: see our Measuring and Modeling Sky Glow Light Pollution page
2. Luginbuhl et al., 2014; Aubé et al., 2013: see our Lamp Spectrum and Light Pollution page
3. Luginbuhl et al., 2009, From the Ground Up I: Light Pollution Sources in Flagstaff, Arizona: see our Measuring and Modeling Sky Glow Light Pollution page
The implication of these figures is clear – lighting complying with good shielding, spectral and amount standards can have dramatically less adverse impacts on the sky and other properties. Choosing minimum reductions from the ranges described above (i.e. 50% due to shielding, 70% due to spectrum, and 25% due to lighting amount), sky glow can easily be reduced 90% – to 1/10th that seen without regulation. Similar dramatic reductions can be achieved for other adverse impacts such as glare and trespass. And all this is achieved with no compromise to utility or safety. There is much to be gained from lighting codes.
As an often critical matter in the application and enforcement of lighting codes where community legal, lighting design, and enforcement resources or expertise are nearly always very limited, lighting codes based on easily quantifiable aspects of lighting use most directly related to cross-boundary impacts are much more efficient, requiring much less expertise and fiscal resources to administer. The codes offered as models below specify shielding, lamp type and amount standards that are demonstrated to be easily and effectively interpreted, applied and enforced without specialized technical training. Lighting codes using lighting design measures such as illumination levels or illumination uniformity are much more difficult to administer, require technical expertise to interpret, implement and enforce, and do not directly address light pollution impacts of general community concern.
Though the standards necessary to achieve good light pollution control are conceptually simple, writing a technically accurate and effective lighting code is not simple. If your community is seeking effective solutions to the problems created by common careless lighting practice, we highly recommend using a code such as listed below that has been tested and found technically sound and effective.
Model Lighting Codes
Before you use a Model Lighting Code…
In 1989 innovative lighting codes were developed for Flagstaff and Coconino County that, in addition to effective standards for shielding and lamp type, were the first to restrict the amount of light permitted (per acre) in outdoor lighting installations. Their intent is to encourage lighting practices and systems that will:
- minimize artificial sky glow, glare, and light trespass;
- conserve energy and resources while maintaining night time safety, utility, security, and productivity; and
- curtail the degradation of the nighttime visual environment.
These lighting codes remain the only codes demonstrated through research and critical dark-sky analysis to actually reduce sky glow light pollution. If your community seeks to protect dark skies, the Flagstaff Dark Skies Coalition strongly recommends using these codes – particularly the Flagstaff and Coconino County codes or models based on them.
(see the updated Pattern Outdoor Lighting Code v2.0 July, 2010.)
These codes work. The critical general limits of 100,000 and 50,000 lamp lumens-per-acre (equivalent to about 70,000 and 35,000 fixture lumens-per-acre) and practical shielding standards have been in place for over twenty years. Hundreds of developments have been successfully built, including service stations, auto dealers, and national retail franchises (Home Depot, OfficeMax, Staples, Target, WalMart SuperCenter, Best Buy, Kohl’s, etc.).
Other codes offered by the lighting industry and other authorities in dark sky protection in collaboration with the lighting industry have not been shown to assure real protection. Critically, analysis by C. Luginbuhl at the US Naval Observatory of the Joint IES-IDA Model Lighting Ordinance4 (MLO) indicated that this “model” will not protect dark skies. The analysis indicates that the MLO allows substantially greater light pollution than these northern Arizona codes and, in most cases, greater light pollution than produced by even unregulated outdoor lighting. The IES-IDA MLO does not effectively address shielding or lighting amounts, and does not address lamp spectrum at all.
Note: Though there are dozens of lighting codes around the US that establish lumens per acre limits following the pattern of these local innovative lighting codes, the Flagstaff Dark Skies Coalition cannot recommend any of these as guides. Most or all have been substantially modified with the frequent introduction of lighting technical, legal and other errors; many have dramatically raised the lumen caps to the point where there will be no effective improvement over otherwise unregulated lighting. Any community using one of the codes recommended here as a base for their code should modify these codes with extreme caution. The IDA Outdoor Lighting Code Handbook provides good general guidance and background for anyone seeking to effectively tailor a lighting code to meet local priorities.
4. Though the IDA-IES MLO states (pg. 4) that it was “developed as a joint under-taking by the Illuminating Engineering Society and the International Dark-Sky Association,” of the nine members of the “joint task force” responsible for the MLO’s development, seven are directly associated with the lighting industries, including both of the co-chairs and three of five nominally representing IDA. It seems obvious to FDSC that regulations to protect night skies and the public from the deleterious effects of outdoor lighting should be informed by responsible lighting practices, but should not be written by the lighting industry.
Some Very Good Codes and Information
Flagstaff AZ Lighting Code [IDA International Dark-Sky City] (updated Nov 2011) Official Title Flagstaff Zoning Code, Chapter 10-50 Division 10-50.70, and parts of Chapters 10-20 (Administration, Procedures and Enforcement), 10-50.100 (Sign Standards), and 10-80 (Definitions) Link is to unofficial copy
Cottonwood Lighting Code (adopted/amended 2000) Official Title: City of Cottonwood Zoning Ordinance, Section 408
Sedona Lighting Code [IDA International Dark-Sky City] (adopted/amended 2001) Official Title: Sedona Land Development Code, Article 9, Subsection 911.01
Coconino County AZ Lighting Code (adopted/amended 2001) Official Title: Coconino County Zoning Ordinance, Chapter 17