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Wasted Lighting: This shows spill light from a sports field at midnight when the field is not in use – light from the field illuminates the building across the street. An OLC curfew and shielded light would save energy, reduce light trespass and more efficiently light the field.

Because of the glare from the unshielded light, the person standing in the gate is not visible in the top image; the light has to be blocked (bottom) to see the intruder. Shielding light and reducing glare will improve safety. (credit: G. Fleenor)

Ensure that outdoor lighting shines where needed — on the ground — rather than being wasted upwards and sideways through poor shielding. Shielding means you can use fewer and/or less powerful lights yet provide improved visibility.

Skyglow caused by LED lights (top) compared with sodium lamps (bottom). White LEDs – all types/CCTs – emit more blue and green light which the human eye is more sensitive to at the low brightness of the night sky. This increases skyglow relative to sodium lamps, erasing stars from the night sky. (credit: Flagstaff Dark Skies Coalition)

Outdoor Lighting Ordinances Make a Difference and Protect Dark Skies

Local governments can foster good outdoor lighting practices with appropriate codes and ordinances.

An outdoor lighting code can ensure “best practices” are followed in providing effective, safe outdoor lighting. A well-written ordinance, with recommendations for good design, will result in secure and economical nighttime lighting while protecting dark skies. AzAC has created a Model Outdoor Lighting Code to assist municipalities in developing a modern dark-sky lighting code or ordinance. For a PDF copy click here; for an editable MS Word file please contact us.

Flagstaff adopted the first outdoor lighting ordinance in 1958. Tucson/Pima County did so in the early 1970s. The State of Arizona, all counties, and many municipalities now have some form of regulation. These have made a substantial difference. Most of these measures, however, need to be updated to provide effective dark sky preservation in the 21st century.

Rapid population growth and changes in lighting technology, especially light emitting diodes, call for updated ordinances and better enforcement. It is critical to address this problem now.

Better Lighting Codes for Arizona ensure a Brighter Future

Improved lighting policies should include these goals to provide economic and practical benefits:

• to ensure that outdoor lighting shines where it’s needed — on the ground — rather than being wasted,
• to promote the use of the most efficient types of lighting,
• to use lighting when and where it’s most needed,
• to only use as much light as is necessary,
• to use the right type of lighting, and
• to make certain the Lighting Code is enforced.

Proper lighting matters to everyone — scientists, business owners, policymakers, and, most importantly, to you.

LEDs & Outdoor Lighting

As older outdoor lighting systems, especially streetlights, reach the end of service life, many municipalities are considering newer, energy efficient, light emitting diodes (LEDs) systems. More than energy savings, however, need to be considered when specifying such an expensive and long-lasting system.

Other considerations include safety, security, cost savings from “smart” system controls, good design including shielded lights, durable equipment, and not least, the color of the light.

The International Dark Sky Association has developed a set of recommendations for municipalities considering the installation of LED outdoor lighting systems available for policy makers from our Resource list below.

AzAC urges city and town officials and staff to seriously consider these recommendations before converting to an LED outdoor lighting system.

Using the Right Type of Outdoor Lighting

The International Dark-Sky Association notes:  Because of their reported long life and energy efficiency, LEDs are rapidly coming into widespread use, replacing the existing lighting in many cities. However, there are important issues to consider when making such a conversion. See the LED Practical Guide for more information.

A drawback of all white LED sources is much brighter sky glow.  In areas near dark sky sensitive sites, narrow-band amber LEDs should be used.

LED lights can be dimmed.  A “Smart” or “Adaptive” Lighting system can allow a city to adjust lighting levels to meet traffic and activity needs. Substantial energy savings can be made by using only the amount of light necessary when it’s needed.  Careful analysis should be made by city officials to evaluate entire system lifetime costs, however, when considering an LED streetlighting system.

Help preserve Arizona’s preeminent research industry, high-tech jobs, and extraordinary natural environment by protecting dark skies.

Retrofitting Factors to Consider

In most cases LED Outdoor Lighting retrofits are done primarily to save money, both operating and maintenance costs. So the people making these decisions often choose the fixtures that will deliver maximum efficacy with little regard to the color of the LED.

A few years ago the typical LED streetlight was in the 6,000K CCT range because it was the only way to compete with HPS. As LED efficacy improved, 4,000K CCT became the new standard. Further improvement has led to the availability of 3,000 CCT and 2,700 CCT LED streetlights. AzAZ recommends 3,000 CCT for general street lighting and 2,700 CCT in dark sky zones.

Missing in the streetlights selection process is a consultation with the “client” regarding what LED is best for their neighborhood. In the world of professional lighting design, it would be unheard of to install a lighting system without consulting the client, who in the case of municipalities, is the resident. The residents ultimately pay the bills and live with the consequences. Not involving them in the design process can be a serious and costly mistake.

Why Color Matters

Since color matters, especially in astronomy, the AzAC Outdoor Lighting Code calls primarily for amber color lighting in Astronomical Resource Zones (i.e. locations near observatories). Because LED lighting creates many times more sky glow than traditional light sources, fully-shielded LPS or HPS fixtures remain the best choices to preserve dark skies.

LED Lighting Systems Practical Guide

Why Color Matters:  Designing Street lighting for the Real Client

Lessons Learned in Davis, Calif. LED Streetlight Retrofit 

Davis Will Spend $350,000 To Replace LED Lights After Neighbor Complaints    

The Natural Night Sky & Artificial Light

High brightness, white light emitting diodes (LEDs) are emerging as a new light source. These have never been applied on a broad scale, and may have unexpected consequences if widely used for outdoor lighting.

The stronger blue emission produced by white light sources, such as LEDs has been shown to have increased negative effects on astronomy and sky glow, and has a greater impact on animal behavior and circadian rhythms than other types of light.

Widespread installation of white light sources rich in blue emission can damage dark skies. Therefore, lamp choices made today, such as streetlights, will affect night lighting for many years to come.

Astronomical Resource Zones

AMA Adopts Community Guidance to Reduce the Harmful Human and Environmental Effects of High Intensity Street Lighting

Arizona Astronomy Coalition Sign Illumination Standards

The Sign Illumination Standards in the AzAC Model Outdoor Lighting Code are part of the overall Code design. A jurisdiction’s Outdoor Lighting Code needs to generally conform to the AzAC Model OLC for these sign standards to work as intended.

Common forms of sign lighting regulation
(Some appear in an OLC; others – e.g. size – are more commonly in a Sign Code.)

Internally illuminated signs

  • Sign size (larger signs emit more light)
  • Sign color (darker colors emit less light)
  • When illuminated?   (curfew)

Externally illuminated (floodlit) signs

  • Sign size (larger signs require more light)
  • Type of light fixtures (fully shielded)
  • How mounted? (top mounted)
  • How much? (lumens limit)
  • When illuminated? (curfew)

Multicolor changeable-copy LED (electronic message) signs

  • Sign size (larger signs emit more light)
  • How much? (nits limit)


The use of opaque or colored backgrounds for internally illuminated signs keeps the light emission within acceptable limits. Limiting light emission through such standards is a practical approach that eliminates the need to verify lumen outputs of lighting contained within the sign cabinet. Regulations allowing for generally brighter signs may require sign lighting to be included in a lumens cap.

The AzAC OLC sets 100 nits as the maximum night time lighting level for multicolor changeable-copy LED (“Electronic Message Center” (EMC)) signs. Surveys of conventional (externally floodlit) billboards show that the vast majority of such signs are illuminated to 100 nits and less, so this standard for LED signs is compatible with current sign design practice. If the nit level of multicolor changeable-copy LED signs were set higher than 100 nits, then smaller sign size and/or darker color composition regulations should be considered.

The curfews respect close-of-business times.

Selected AzAC Model OLC sections follow:

Section 5: Outdoor Lighting Standards

Section 6. Outdoor Advertising Sign Lighting Standards

Section 10. Prohibitions

and Section 17. Definitions

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