RMLUI Legal Corner: Opening Up the Universe with Dark Skies Regulations

Night sky image. Photo by the Arkansas Oklahoma Astronomical Society. Copyright © 2007 Mike Holloway. All rights reserved.

Night sky image. Photo by the Arkansas Oklahoma Astronomical Society. Copyright © 2007 Mike Holloway. All rights reserved.

by Elizabeth Garvin,1 AICP, Denver, Colorado

Do you remember the first time you saw the Milky Way? I do. My husband and I were driving through northern Oklahoma at night, and I looked through the sunroof of the car to see the sky in a way that I had never noticed before. Happily for me I was in Oklahoma where you can see the night sky like the image below. I thought it was pretty stunning and much more interesting than the snooze-inducing lecture we had recently attended at a famous planetarium.

Not every place in our country offers the same view, though, because our nighttime lighting choices can get in the way of seeing the sky. For some communities, nighttime lighting reflects local character and is an important part of the community’s image, such as in Reno or Las Vegas, Nevada. Other communities and states, including all of New Mexico, pursuant to their early adoption of the Night Sky Protection Act in 1999, along with Tucson and Flagstaff, Arizona, prefer to dim the human lighting at night and take in a more celestial view. If that is a choice your community is considering, read on for an overview of the most common current approaches to preparing a dark sky ordinance.

What Does a Dark Sky Ordinance Regulate?

Light pollution. In simplest terms, when we allow our light sources to brighten the sky outside of the lighting task that they were designed to do, we may create light pollution. According to the Lighting Research Center at the Rensselaer Polytechnic Institute, light pollution has three main sources:

  1. Sky glow, which is a brightening of the sky caused by both natural and human factors
  2. Light trespass, which is light that is cast where it is not wanted or needed, such as from a streetlight into a home
  3. Glare, which is objectionable brightness2

Model Dark Sky Regulations

Defining and understanding light pollution is not all that complicated; drafting proper local regulations to address light pollution can be. Outdoor lighting regulations should include basic standards for the shielding of light fixtures, spectrum of light sources, and amount of permissible light.3 There are a number of dark sky model regulations, and many locally adopted regulations, which a community can adapt4 as the basis for local regulations.

The key difference in these model codes is determining appropriate lighting measurement standards. Here’s the lecture: Figure out the best model for your community and start there. The “most-fabulous-and spectacularly-trendy-regulations” may not be the best for your community. Why?

  1. Some model regulations may not fit with your approach to regulation, for example, your community may appreciate regulatory flexibility while the model has rigid standards.
  2. Some model regulations may require an administrator with a specific educational background or the purchase of expensive measurement tools, issues that caused problems back in the heyday of performance zoning.
  3. Some model regulations may not be regulated to achieve a specific result that lines up with your community’s goals.

For most zoning issues, there are good regulations all along the basic-to-complex spectrum. When choosing a model code which to refine into local regulations, planners should pay attention to the Three Development Standards Abilities:5

  1. The ability of development professionals to understand the regulations
  2. The ability of planning staff to interpret and administer the regulations
  3. The ability of elected and appointed officials to review and approve plans based on the regulations

If the proposed regulations function below or above your community’s Three Development Standards Abilities, you may not get the results you anticipate. This moves you very quickly from a list to a law - Murphy’s Law.

International Dark-Sky Association (IDA)6

This is not really a model code but some basic guidelines for creating standards. The key message of the guidelines is use less light. The core measurement standard is this:

“All lighting installations shall be designed and installed to be fully shielded (full cutoff), except as in exceptions below, and shall have a maximum lamp wattage of 250 watts HID (or lumen equivalent) for commercial lighting, 100 watts incandescent, and 26 watts compact fluorescent for residential lighting (or approximately 1,600 lumens). In residential areas, light should be shielded such that the lamp itself or the lamp image is not directly visible outside the property perimeter.”

A list of exceptions is provided, such as lighting required by building codes or low voltage landscape lighting and key definitions are included. Communities are on their own to determine how to convert these recommendations into objective standards.

Pennsylvania Outdoor Lighting Council7 (POLC)

This model ordinance appears to be intended to take local governments from no or minimal lighting regulations to a more comprehensive but easy-to-decipher regulatory approach. According to a supporting PowerPoint available on the POLC website, a good lighting ordinance does three things:

  • Prevents excessive and under lighting
  • Protects citizens, drivers, the environment, and the night sky from light glare and light pollution
  • Sends a clear message that bad lighting will not be tolerated

The heart of the POLC model is the creation and submission of a complete lighting plan for the site that identifies a detailed list of lighting items to be identified, located, and/or measured across the site. The regulations then establish the objective standards for fixture types, glare control, illuminance levels, light mounting height, shut-off hours, and compliance monitoring, against which the lighting plan is measured. The model ordinance is supported on the POLC website by an excellent explanation of why lighting ordinances are important, how to build support for the ordinance across the community, and how to enforce the regulations,8 along with PowerPoint presentations that explain how the regulations work.

Background on the Next Two Codes

The IDA is an advocacy organization for all things dark sky. According to their website: “The International Dark-Sky Association is the only non-profit organization fighting to preserve the night.” The IDA was founded in 1988 to promote the idea of “light what you need, when you need it.”9 In 2002, the IDA published the USA Pattern Code as a model outdoor lighting ordinance. The USA Pattern Code served as the basis for successful dark sky regulations in a number of communities, including Flagstaff and Coconino County, Arizona. Over time, the IDA decided to develop a new model code, called the Model Lighting Ordinance (MLO), and they dropped their support for the USA Pattern Code. The MLO proved somewhat controversial, however, and has been subject to studies and assertions that conclude that the MLO permits much more light pollution than the USA Pattern Code did. The USA Pattern Code was rescued by an advocate at the U.S. Naval Observatory10 and updated to its current format as the Pattern Outdoor Lighting Code Version 2.0.11

Pattern Outdoor Lighting Code Version 2.012

The Pattern Code represents the next level lighting regulation detail beyond the POLC model. The Pattern Code establishes two lighting zones within the community and then specifies total outdoor light output and light shielding requirements by land use by light zone across the community. Permitted lamp types (incandescent, fluorescent, CFL, etc.) are identified by lighting type by land use in this model that makes very good use of tables and graphics.

The Pattern Code is based on a regulatory shift from the POLC Model. In the POLC Model, the lighting plan is the focus of the code and probably serves to highlight unanticipated issues that the code is not sufficiently detailed to address but that can be addressed as part of the development approval. In the Pattern Code, detailed standards are identified within the body of the regulations and the lighting plan acts as more of a compliance check.

The Pattern Code also includes standards for outdoor advertising signs, including multicolor changeable copy LED Signs (100 nits maximum at night required to be dimmed by automatic control, no messing around here!). Special use lighting standards include recreational facilities, automobile dealer displays, and service station canopies. As with the POLC model, the Pattern Code requires the submission of a lighting plan but the detail required by the Pattern Code is not as extensive as that required by the POLC model. An extensive, illustrated definition section is provided in the Pattern Code that translates may specialized lighting terms into easier to understand concepts.

Joint IDA-IES Model Lighting Ordinance13

The new(ish) MLO was developed jointly by the IDA and the Illuminating Engineers Society. One of the important aspects of this collaboration was to create a model code that “can be met using readily available, reasonably priced lighting equipment.” Some commentators have noted that the world of light design and production has seriously lagged the adoption of dark sky regulations14 and so this approach may be helpful to some communities.

The MLO takes a two-part, optional approach to designing lighting. The code establishes five lighting zones that range from wilderness areas to entertainment districts and specifies the character of ambient lighting permitted in each district. According to the commentary in the code, the regulations “limit the amount of light that can be used, but do not control how that lighting is used.”15 Applicants with non-residential development are then allowed to choose whether to follow the Prescriptive Method to seek approval that is based on fairly objective standards, or the Performance Method that allows “greater flexibility and creativity in meeting the intent of the ordinance.”16Selection of the performance method appears to require the use of an engineer or lighting professional, and the code recommends that the reviewing jurisdiction may wish to also hire an engineer or lighting professional to review the plan.

The MLO also includes basic standards for residential lighting that includes landscaping lighting. In the Lighting by Special Permit Section, the MLO provides that certain lighting uses require a special use permit but only provides minimal review standards for this process. For communities seeking both basic standards and options for site lighting design negotiation, the MLO provides both.

This brings me to my last point about using model regulations – laws vary from state to state and it is critical to make sure that the regulations your community will adopt comply with all federal, state, and local legal requirements. In the MLO, I found the special permit decision-making criteria section to be lacking from a legal perspective in that it provided insufficient guidance for either applicants or decision-makers. I also scribbled a note in the margin of Section VII.A that appears to require amortization for existing lighting that does not comply with the new standards, thinking somewhere in the legal mists in my memory that not all states permit amortization. And finally, the General Notes in Adopting this Model Ordinance section appears to run roughshod over procedural due process standards when it states that “[a]doption of this ordinance should follow the established development, review, and approval processes of the adopting authority. If no such processes are in place, this ordinance may be adopted as a new independent section of the Municipal Code.” If no ordinance review and approval processes are in place, your community may have bigger problems than deciding how to make the night sky darker. Take the advice of your staff attorney for all legal matters, not the instructions of the model code drafter.

Elizabeth Garvin, AICP, is an attorney with Spencer Fane Britte & Browne. She serves on the Regional Board for the Rocky Mountain Land Use Institute.


  1. Elizabeth is an attorney with Spencer Fane Britt & Browne in Denver. The materials in this column do not constitute legal advice, do not necessarily reflect the opinions of the RMLUI, and nothing provided herein should be used as a substitute for advice of local counsel. This column is not intended to act as a solicitation or advertisement. I would like to dedicate this column to my young friend Christian C. who likes to think about the universe.
  2. http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/lightpollution/lightpollution.asp
  3. Flagstaff Dark Skies Coalition, Outdoor Lighting Codes, http://www.flagstaffdarkskies.org/dark-sky-solutions/dark-sky-solutions-2/outdoor-lighting-codes/
  4. “Adapt” means to revise to fit the needs of a specific community. It does not mean “take these regulations, search and replace with your community’s name, then adopt.”
  5. This is a valid regulatory drafting concept, I just gave it the new catchy name.
  6. http://www.darksky.org/lighting-codes/simple-guidelines-to-lighting-regulations
  7. http://www.polcouncil.org/polc2/municipal.htm#ModelOrd
  8. http://www.polcouncil.org/polc2/municipal.htm
  9. http://www.darksky.org/about-us
  10. Christian Luginbuhl. See, http://www.nofs.navy.mil/about_NOFS/staff/cbl/ to learn more about Mr. Luginbuhl’s work in outdoor lighting.
  11. For further discussion of both codes, see Outdoor Lighting Codes on the Flagstaff Dark Skies Coalition website (http://www.flagstaffdarkskies.org/) and Outdoor Lighting Ordinances: Proven Alternatives to the MLO” on the Illinois Coalition for Responsible Outdoor Lighting website(http://www.illinoislighting.org/).
  12. http://www.nofs.navy.mil/about_NOFS/darksky/CL_POLC_standard_v2.0.pdf. I’m not sure if anybody has noticed that the Pattern Outdoor Lighting Code and the Pennsylvania Outdoor Lighting Council share the same acronym. We will refer to the Pattern Outdoor Lighting Code as the “Pattern Code” in this article.
  13. http://www.darksky.org/outdoorlighting/mlo
  14. See Jennifer Pinto, New Developments in Dark Sky Compliant Lighting, Residential Lighting http://www.residentiallighting.com/new-developments-dark-sky-compliant-lighting
  15. MLO Section IV. Non-Residential Lighting – User’s Guide.
  16.  Id.

Published in the April/May 2015 Issue

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