HomeMy WebLinkAbout09-03-25 Public Comment - B. Rice - Comments on Bozeman UDC process - Preservation of the Night SkyFrom:Bonnie Rice
To:Bozeman Public Comment
Subject:[EXTERNAL]Comments on Bozeman UDC process - Preservation of the Night Sky
Date:Wednesday, September 3, 2025 11:02:16 AM
Attachments:Comments re Bozeman UDC Dark Sky Preservation - September 2025.pdf
DarkSky MOR-007b_2025_Bozeman July 2025.pdf
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Dear Bozeman Community Development Board and City Commission:
Please accept the attached comments in regard to the update of Bozeman's development code,on behalf of myself and Dr. Joseph Shaw, Director, Optical Technology Center at Montana
State University. Please do not hesitate to contact me if you have any questions.
Thank you,
Bonnie RiceBozeman, MT
(406) 640-2857bjrice16@gmail.com
To: Bozeman Community Development Board and City Commission
Re: Update of Development Code - Dark Sky Preservation
Date: September 3, 2025
From: Bonnie Rice,
Dr. Joseph Shaw – Director, Optical Technology Center (OpTeC), Montana State
University
Sent electronically via: comments@bozeman.net
“Appreciation for dark skies is entering the social consciousness. Light
pollution is one of the only types of pollution that’s completely and
immediately reversible. I don't think we’ll realize the value of seeing the
Milky Way, until it’s gone.” – Bettymaya Foott, Dark Sky International
Dear Members of the Community Development Board and City Commission:
We write to you today as community members concerned about light pollution and preservation
of the night sky in Bozeman, the Gallatin Valley, and beyond. The City’s ongoing public process
to update its Development Code presents an excellent opportunity to help address goals and
directives contained in Bozeman’s Outdoor Lighting Code, the Gallatin Valley Sensitive Lands
Plan, and the Gallatin Valley Growth Policy to preserve the night sky and to prevent and reduce
pollution from artificial light. Preservation of the night sky is a community value and was raised
by community residents in the public engagement meetings regarding the update of Bozeman’s
development code in the spring of 2025. As has been well documented, Bozeman and the
Gallatin Valley are experiencing unprecedented population growth with no end in sight, with
associated housing and infrastructure development and services attempting to meet the
demands of our growing population. All of this raises profound implications for preservation of
the night sky and the health and well-being of people and ecosystems in the Gallatin Valley and
beyond. We are in danger of losing our night sky and all of the benefits that a dark sky provides.
Preservation of the night sky is also important to the economy of Bozeman and the Gallatin
Valley. As explained further below, the Montana State University (MSU) Optical Technology
Center was established in the early 1990s to promote optics/photonics education and research
for economic development, and there are now more than 40 photonics companies here. A key
competitive advantage for MSU photonics research is the natural Montana environment,
including our dark sky.
We urge you – as members of the Community Development Board and City Commission – to
ensure that preservation of dark skies is an integral component in the current UDC process and
other ongoing community processes and policies related to growth and development in
Bozeman and the broader Gallatin Valley.
I. Introduction
Recognizing the need to protect the night sky and provide guidance and directives regarding
lighting, Bozeman developed an outdoor lighting code (Division 38.570) in the early 2000s. One
of the code’s stated purposes is to preserve the night sky:
“[P]rotect neighbors and the night sky from nuisance glare and stray light from poorly
aimed, placed, applied, maintained or shielded light sources;” (38.570.010 “Purpose”)
There are several excellent elements in the code to help prevent or reduce artificial light
pollution. However, there are also large areas that are not covered by the code in regard to
outdoor lighting, and there have been many innovations in the lighting industry since the early
2000s when Bozeman’s code was developed. Additionally, an ever-growing body of scientific
research continues to document the benefits of dark skies and the negative impacts of light
pollution. Bozeman should take concrete steps to update its lighting code to incorporate these
industry innovations and scientific research, and work with the City of Belgrade and Gallatin
County policy makers to develop and enact policies that will preserve the night sky in the
broader Gallatin Valley.
Dark Sky International (DarkSky, formerly the International Dark Sky Association) is the primary
organization working to preserve dark skies and to reduce artificial light pollution around the
world. A growing number of municipalities, states and countries are partnering with DarkSky to
preserve their night skies. To that end, we have contracted with DarkSky to evaluate
a) Bozeman’s Municipal Code in regard to outdoor lighting (Division 38.570), and b) Bozeman’s
Design and Construction Standards Standard Specifications for Lighting Materials and
Installation (Revision March 2020) specifically regarding streetlights and lighting adjacent to
roadways, in order to assist City and County staff, elected officials, and others in identifying
where the existing code and standards are already strong and where they could benefit from
improvements to achieve the City’s stated goal of preserving the night sky. That analysis is
attached. While there are strong elements to the existing code/standards, there are numerous
areas where Bozeman’s outdoor lighting code needs to be updated and improved in order to
truly protect the night sky and to prevent artificial light pollution and light trespass. Key areas
where Bozeman’s code falls short are highlighted below in this document.
II. What is Light Pollution?
DarkSky defines light pollution as “any adverse or unintended effect of the use of artificial light
at night, including sky glow, glare, light trespass, light clutter, decreased visibility at night, and
energy waste." Many of us think about light pollution as the inability to see the stars, especially
in cities, but light pollution includes other sources such as glare on roadways at night, or light
from a neighbor’s residence that shines into our bedroom, or light that shines into wildlife
habitat.
The good news is that – unlike many other types of environmental pollution – light pollution can
be solved relatively easily, many times with a flick of a switch. DarkSky has five principles for
lighting that can prevent or greatly reduce light pollution: Make sure it is useful and necessary;
Target the light; Use the lowest level required; Use controls such as timers or motion detectors
so light is available only when needed; and Utilize warm-colored light.
III. Importance and Benefits of Preservation of the Night Sky
According to DarkSky, artificial light pollution is increasing globally by an astounding 10% per
year. Not being able to experience the awe and wonder that come with gazing up at a star-filled
sky, and pondering our place in the universe, would be a deep loss. Today, approximately 80%
of people in the U.S. are no longer able to see the Milky Way due to light pollution.
Preservation of dark skies is critical for many other reasons as well. For billions of years, all life
has relied on Earth’s predictable rhythm of day and night. It’s encoded in the DNA of all plants
and animals. Humans have radically disrupted this cycle by lighting up the night. Research
shows that artificial light at night has negative and even deadly effects on many species. Light
pollution disrupts wildlife, impacts human health, wastes money and energy, contributes to
climate change, and blocks out our view of the universe.
Plants and animals depend on Earth’s daily cycle of light and dark to govern life-sustaining
behaviors such as reproduction, nourishment, sleep, and protection from predators. Two-thirds
of invertebrates such as insects are either wholly or partially nocturnal, relying on darkness to
fulfil their roles including pollination. Light pollution interferes with reproduction, increases
predation, and disorients migration for species such as monarch butterflies and others that
navigate using the stars and Moon. Birds also rely on the stars and Moon for navigation.
Lighting up the sky can cause them to migrate too early or too late, or to wander off course, or
to collide with buildings – often leading to exhaustion and death.
Humans are profoundly impacted as well. Many studies have shown that exposure to artificial
light at night negatively affects human health, including increased risk for obesity, depression,
sleep disorders, diabetes, breast cancer and more. Like most life on Earth, humans adhere to a
circadian rhythm — our biological clock — a sleep-wake pattern that is governed by the natural
day/night cycle. Artificial light at night can disrupt that cycle. Nighttime exposure to artificial light
also suppresses melatonin production, which we need to stay healthy.
IV. Relevance of Dark Sky Preservation to Bozeman/Gallatin Valley Municipal
Code, Plans and Policies
a. Bozeman’s Outdoor Lighting Code (Municipal Code, Division 38.570)
Three of the five goals enumerated in the “Purpose” section (Section 38.570.010) of Division
38.570 in regard to outdoor lighting address preservation of the night sky, nuisance from
artificial light, and energy conservation:
“[P]rotect drivers, bicyclists and pedestrians from the glare of non-vehicular light sources
that shine into their eyes and thereby impair safe travel;
Protect neighbors and the night sky from nuisance glare and stray light from poorly
aimed, placed, applied, maintained or shielded light sources;”
and
“[P]revent excessive lighting and conserve energy.”
Section 38.570.020 (“General”) states that “Unless otherwise approved through a planned unit
development, this section applies to all lighting for subdivisions, land uses, developments and
buildings. In addition, any site modification that requires a certificate of appropriateness, site
plan review or reuse application will necessitate compliance for all existing and proposed
lighting on the site.”
b. Gallatin Valley Sensitive Lands Plan
As noted in the Gallatin Valley Sensitive Lands Plan Section 2.2. Dark Sky Lighting,
“[D]ark sky lighting is increasingly important as growth continues in the valley.
Lighting is an important safety feature in neighborhoods and can extend the use
of amenities after dark, especially during the summer. However, artificial lighting
can affect animals that sleep at night and can be disorienting for nocturnal animals
and insects, including pollinators like moths. Artificial lighting can also disrupt
reproduction and mating cycles; benefit predators to the detriment of their prey;
alter migration routes; cause foraging avoidance for many species; and result in
building collisions, in the case of birds. In some cases, artificial lighting has also
caused mammals to avoid typical habitat areas all together. Light fixtures should
be selectively placed, hooded/shielded (i.e., not emitting direct or indirect light
above an imaginary horizontal plane passing through the light source), and directed
downward and away from nearby natural areas. In areas with evening activities that
require lighting, such as sports fields, rodeos, and event centers, the location and
timing of activities should be considered and lights should be turned off when not
needed. Light fixtures with motion or heat sensors may be used to keep lights off
when lighting is not required.
In addition to the location and type of fixture, it is important to consider the physical
properties of the light that is produced. The International Dark Sky Association
(IDA) recommends using lighting that has a color temperature of no more than
3000 Kelvin. The IDA has developed the Fixture Seal of Approval program to
provide objective, third-party certification for lighting that minimizes glare, reduces
light trespass, and doesn’t pollute the night sky. Gallatin County and the City of
Bozeman’s standards for lighting in some areas do meet these recommendations.”
c. Gallatin County Growth Plan
Recognizing the importance of dark sky preservation to public health and safety, the natural
environment, wildlife and wildlife habitat, Gallatin County’s Growth Policy calls for development
of a policy to:
“[D]evelop and implement a dark sky policy to address light pollution and preserve our
night skies.” (p.7.12)
and:
“[E]ncourage development to conserve and emphasize scenic resources and views
including preservation of ridge tops and hillsides and protection of dark skies.” (p. 7.17)
In regard to future land use guidelines, and design standards, the Growth Policy includes
direction to:
“[M]itigate the impact of uses on neighboring properties or at the growth area
boundaries, such as dark skies standards, landscape buffers, and other measures to
reduce noise and light pollution.” (p. 8.16)
And in regard to the Policy’s section on the Natural Environment:
“[T]he following items may be considered when evaluating a proposed subdivision’s
potentially significant adverse impacts on the natural environment:
[...L]ight pollution on adjacent property.”
As recognized in these policies, preservation of the night sky and prevention of artificial light
pollution are critical to human and wildlife health, and to the economy, ecology, and intrinsic
character of Bozeman, the state of Montana, and the Greater Yellowstone Ecosystem.
V. DarkSky Analysis of Bozeman’s Outdoor Lighting Code (Division 38.570)
and Design and Construction Standards (Revision March 2020)
Overall Assessment
“[D]arkSky commends Bozeman on having a lighting ordinance, there were many good
characteristics within. The purpose section was very strong and met DarkSky
expectations. The sports lighting section was also strong, stronger than most, but fell just
shy of meeting the exact DarkSky requirements. Other sections met about 50% of
DarkSky expectations. Missing mandatory elements include applicability to residential
and planned unit developments along with, at a minimum, a compliance trigger authority
for hazards to public safety. Also missing are elements related to the five principles for
responsible outdoor lighting, including some over-lighting protections based on lighting
standards that are more current than 1998, and very high-angle glare reduction above
80°.”
DarkSky analysis of specific components of Bozeman’s outdoor lighting code, and where it
needs to be strengthened to meet today’s lighting standards and preservation of the night sky,
follow below.
The largest issues include:
- Street lighting and adjacent public right-of-way are addressed in the Design and
Construction Standards. However, properties not adjacent to roadway and residential
property are not listed within the scope for new and replacement lighting sources, and
planned unit developments (PUDs) appear to be exempt from this ordinance but should
be included. Residential lighting is one of the biggest sources of light pollution.
- 38.570.040 provides some, but not all outdoor lighting levels found in Illumination
Engineering Society (IES) standards. And, unfortunately, the items listed are from 1998,
some of which are excessive by 2022 standards (e.g., building entrances at 50 lux
instead of RP43's 1 to 30 lux range).
- Bozeman’s code does not have a limitation of 3000 Kelvin Correlated Color Temperature
(CCT), a measurement used in lighting to describe the color appearance of light emitted
by a source and indicates whether the light appears warm (yellowish) or cool (bluish).
Blue light contributes more to light pollution and increased glare than warm light, and
has been shown to affect human health and wildlife behavior. A limitation of 3000K is
very important to limiting light pollution. (Bozeman’s Design and Construction Standards
do have a 3000K maximum for street lighting and lighting adjacent to roadways, but this
maximum is not part of Bozeman’s Outdoor Lighting Code for all other
development/infrastructure.)
- Bozeman’s code requires no light output emitted above 90 degrees at any lateral angle
around the luminaire fixture; current recommendations reduce that to 80%.
Purpose (Section 38.570.010)
a. Ecosystem Welfare: Bozeman’s code should be strengthened by incorporating language
regarding the hazards of artificial light at night on wildlife and other nocturnal
ecosystems, including habitat and crops.
b. Lighting Zone Responsibility: Some IES standards make illuminance recommendations
by lighting zone (e.g., RP43). The Bozeman ordinance does not mention a community
plan for lighting zones. DarkSky recommends municipalities plan for their nighttime
character and a hierarchy of transitions by assigning a lighting zone overlay or table
Lighting Requirements (Sections 38.570.040 and 38.570.060)
a) 38.570.040 provides some, but not all outdoor lighting levels found in IES standards.
Also, the items listed are from 1998, some of which are excessive by 2022
standards (e.g., building entrances at 50 lux instead of RP43's 1 to 30 lux range).
Additional street lighting measurement methods have been drafted by Clanton &
Associates, are accurate, and listed in the Design and Construction Standards appendix.
b) Fully-shielded lights are mandated, which is very important. However, newer
restrictions above 80° are not identified specifically enough. 38.570.040(G)(4)
comes really close, and could meet the DarkSky requirement by calling for luminaires
with G2 rating of 5% emission above 80°.
c) The maximum CCT is very important and DarkSky was not able to find a maximum
set in the Bozeman code. The maximum should be 3000 CCT.
d) There is no mention of light trespass onto wilderness, wildlife habitat, or sensitive
land/water. As noted above, the Gallatin Valley Sensitive Lands Plan notes the
importance of preservation of the night sky and negative impacts of light pollution on
wildlife and natural ecosystems.
e) In regard to residential light pollution trespass, 38.570.040(G)(5) lists values with no unit.
Assuming footcandles, which matches the rest of the document, these numbers
exceed DarkSky’s recommendations by 300%.
Applicability
a) For new and replacement sources, street lighting and adjacent public ROW are
addressed in the design and construction standards. However, properties not adjacent
to roadway and residential property are not listed within the scope, and PUD's
appear to be exempt from this ordinance but should be included.
b) 38.570.100 is one trigger that forces compliance and 38.570.110 demonstrates the
difference between non-conforming and conforming. However, we do not see a date
for lighting to comply.
Sports Lighting (Section 38.570.050)
a. Containment: 38.570.050(B)-aiming angle and (C)-trespass help this situation, but do
not specifically contain light to field/bleacher area. The property could be very large.
b. Skyward Light Limit: 38.570.050(B) talks about aiming for max candela angle but does
not specifically limit emission above 80°.
c. Appropriate CCT: We did not see mention of limiting CCT for any lighting, including
sports lighting. (as noted above, the Design and Construction Standards do specify a
limit of 3000K for roadways and projects directly adjacent to roadways)
Application Process
a) The permit process (chapter 1.4.1) and the submittal process (chapter 3.2.6) are
documented in the Bozeman Design and Construction Standards. These processes
meet DarkSky expectations for streetlights, but DarkSky would also expect this process
for any lights within the public right-of-way, institutional use, commercial developments,
and sports fields.
VI. Economic Benefits of Dark Sky Preservation to Bozeman, the Gallatin
Valley, and Montana
a. Light Pollution Wastes Money and Resources
One of the most persuasive arguments for improved lighting management is the economic
savings aspect of reduced energy usage. Research shows that globally, outdoor lighting makes
up approximately eight percent of global energy use with about 60 percent of that wasted as
unneeded, overlit or poorly aimed lighting. In the United States, DarkSky estimates that 30
percent of all outdoor lighting is wasted, mostly due to unshielded or excessively bright lights.
This adds up to $3.3 billion dollars wasted annually. Installing quality outdoor lighting could cut
energy use by 60 to 70 percent, saving billions of dollars.
Additionally, light pollution contributes to climate change. Artificial lighting at night and the
energy required to produce it has a large carbon footprint. According to DarkSky, in the U.S.
alone, unnecessary lighting produces 21 million tons of carbon dioxide each year. 875 million
trees would need to be planted annually to offset this waste.
b. The Importance of Dark Skies to Bozeman’s Photonics Industry and Research Economy
Montana State University (MSU) serves as an economic engine for the community,
state, and nation through both student training and technology development. The MSU
Optical Technology Center was established in the early 1990s to promote
optics/photonics education and research for economic development. The goal was to
motivate and encourage graduate students to create high-tech photonics companies so that
they could stay in Montana instead of leaving after graduation. This has been
extraordinarily successful, and the Gallatin Valley is now home to more than 40
photonics companies – one of the highest concentrations of laser and optics companies
in the nation. These companies manufacture materials, components, and systems that
are used in applications from precision agriculture to self-driving transportation to space
exploration.
This entire segment of the Montana economy depends fundamentally on
MSU research for advanced student training and technology development. A key
competitive advantage for MSU photonics research is the natural Montana environment,
including our dark sky. MSU researchers are currently developing numerous photonic
sensor technologies that require testing in nighttime skies that have minimal light
pollution. This provides a strong economic incentive to encourage dark-sky-certified
lighting throughout our community.
c. The Importance of Dark Skies to Montana’s Burgeoning Astrotourism Industry
“Crucially, from an economic standpoint, the single most important thing
about dark-sky tourism is that it necessitates one or more overnight stays.”
– Mitchell and Gallaway (2019)
Montana is fortunate to have many areas where it is still possible to see the Milky Way and a
dark sky. However, we must act now in order to ensure that future generations have the same
opportunities, and to protect the remaining wild ecosystems and world-class wildlife of Montana
from the increasing negative effects of artificial light pollution.
A growing number of cities, states and countries are realizing the economic benefits of
astronomy tourism, or “astrotourism.” Utah is a leader in this arena, with fourteen International
Dark Sky Parks, two International Dark Sky communities and multiple parks and communities
currently working through the accreditation process with DarkSky.
Here in Montana, we have two designated parks – Glacier National Park and Medicine Rocks
State Park. But with over 30 million acres of protected federal and state land and the third-
lowest population density in the U.S., there are many more opportunities to explore the night sky
in Montana.
Following certification in 2020 of Medicine Rocks State Park as an International Dark Sky
Sanctuary – the highest certification possible by DarkSky – a collaborative “Trail to the Stars”
astrotourism initiative was launched by three travel regions – Southeast Montana, Missouri
River Country and Central Montana, with 45 designated star-gazing sites. The initiative won a
national Excellence in Tourism Collaboration Award in 2023.
In April of this year, the University of Montana’s Institute for Tourism and Recreation Research
(ITRR released a study1 with the goal of understanding stargazing tourists and the economic
potential of “dark sky” tourism in Montana, including the newly-designated Trail to the Stars.
They found that:
1https://scholarworks.umt.edu/cgi/viewcontent.cgi?article=1470&context=itrr_pubs&_gl=1*1xr9era*_gcl_a
u*NjczNDU4OTk5LjE3NTQzNDA4NDY.
“...[s]targazing almost always necessitates an overnight stay, as it’s rare for people to
drive long distances to remote locations and then return home in the same evening. This
turns a day visitor into an overnight tourist, with the average stay five nights for those
who come for this niche experience. Those five nights facilitate money spent in the local
economies that support the trail.”
According to the National Park Service, average spending per-party per-day for a local day trip
is $40.63. This rises to over $430 for parties staying overnight in an NPS lodge and a little over
$290 for those staying in motels outside national parks.2
Glacier National Park and its sister park Waterton Lakes National Park in Canada became
International Dark Sky Parks in 2021. A quick internet search reveals many sites targeting dark
sky tourism in Glacier. Closer to Bozeman, the opportunities for night sky viewing in
Yellowstone National Park are increasing, with guiding companies such as Yellowstone Safari
Company offering four-hour star-gazing tours starting at $650.3
Importantly, the ITRR study found that:
“[F]inally, the survey explored respondents’ expectations and assessments of Montana’s
night sky. Over two-thirds (70%) expected to see a “starry night” sky, and 69% agreed
that Montana’s night sky is pristine. Almost two-thirds (65%) valued viewing the night
sky, and 63% believed Montana has a good reputation for it. However, only 44% felt that
observing the night sky was an important part of their Montana experience, and just 23%
visited Montana specifically for this reason. These Institute for Tourism and Recreation
Research results suggest a mismatch between Montana’s reputation for night sky
viewing and the primary reasons for visiting the state.”
This suggests that much more can be done in regard to public education and outreach on
Montana as a prime star-gazing destination experience. Additionally, as noted by the ITRR in a
press release accompanying its study results, “With Montana recently named 2025’s ultimate
stargazing destination by National Geographic, the state has all the reason to put effort behind
causes that help safeguard its “star-studded” reputation.”
VII. Preserving the Night Sky Does Not Mean Sacrificing Public Safety
Although there is a strong tendency to equate more light with safety and security, lighting up the
nighttime environment does not necessarily increase safety and security. “Bright” lighting does
not necessarily mean “safer” lighting. Bright glaring lights create sharp contrast between light
and darkness, making the area outside of the illuminated area hard to see. This contrast can
also create deep shadows that provide concealment. Effective lighting that helps people be safe
2 Mitchell and Gallaway (2016) Estimating the Potential Economic Value of the Night Skies Above the
Colorado Plateau. Missouri State University. Retrieved from:
https://www.cityofpage.org/images/council_mtg_pdfs/2016/July/July27wsminpt.2.pdf
3 https://yellowstonesafari.com/yellowstone-national-park-stargazing/
—not just feel safe—is a win-win situation for everyone. The appropriate use of “dark-sky
friendly” lighting will actually improve overall safety. Lower lighting levels, warmer light
temperatures, and better coverage are safer lighting methods. More information can be found
at: darksky.org/resources/what-is-light-pollution/effects/safety
At home: Poor lighting can create a false sense of security.
Poorly designed outdoor lighting can backfire on safety. Bright and misdirected lights create
shadows for criminals to hide, and some crimes, like vandalism, thrive in well-lit areas.
Floodlights, for example, may highlight potential targets.
In town: Light for light’s sake doesn’t equal increased safety.
While towns, cities, and businesses aim to enhance safety with lighting, poorly aimed and
inadequately shielded lights can attract criminals. A Chicago study identified a correlation
between increased crime and overly bright alleyways.
On the road: Bad lighting creates unsafe driving conditions.
Inadequate roadway lighting causes glare, contributing to accidents, especially affecting older
individuals. A 2015 Journal of Epidemiology and Community Health study revealed that
streetlights don't effectively prevent accidents or crime but they do cost a lot of money.
Poorly designed outdoor lighting can backfire on safety. Bright and misdirected lights create
shadows for criminals to hide, and some crimes, like vandalism, thrive in well-lit areas.
Floodlights, for example, may highlight potential targets.
VIII. Conclusion
Fortunately, light pollution is one of the forms of environmental pollution that can be reversed
virtually immediately, by simply turning off the light where it is not needed, and/or by installing
“dark-sky” friendly lighting and utilizing DarkSky’s five principles of responsible lighting. More
and more communities, states and parks are realizing the substantial benefits of preserving the
night sky and are working to prevent light pollution. Bozeman can join this trend and be a leader
in Montana in preserving the benefits, wonder and awe of a dark, star-filled sky. We urge you to
take action to protect the night sky for future generations and for all species who are an integral
part of the wild and irreplaceable Greater Yellowstone ecosystem.
Sincerely,
Bonnie Rice
Dr. Joseph Shaw
Director, Optical Technology Center (OpTeC), Montana State University
DarkSky Recognized Municipal Ordinance Review
ID Number:Contact Name: Bonnie Rice
Municipality Name:Contact email:bjrice16@gmail.com
State:Contact Phone:406-640-2857
Review Document:Bozeman-Outdoor-Lighting-Code
Y
N
P
= Meets DarkSky requirements
Review Summary:
Previously evaluated in March 2025 as MOR-003b, Bozemen has now submitted their 10/24 COB Design and Construction Standards
(COB-DCS) as a supplemental document capable of fulfilling previously missing ordinance requirements.
Further review by DarkSky and a new review of the COB-DCS did help the Bozeman outdoor lighting ordinance comply with three
previously failed requirements. However, COB-DCS is very streetlighting centric so the opportunity to add additional scope, like non-
adjacent institutional or commercial developments with pedestrian right-of-way, would be required to meet DarkSky's application
requirement. DarkSky continues to commend Bozeman on having a lighting ordinance, there are many good characteristics within.
The purpose section is very strong and meets DarkSky expectations. The sports lighting section is also strong, stronger than most, but
fell just shy of meeting the exact DarkSky requirements. Other sections meet about 50% of DarkSky expectations. Missing mandatory
elements include applicability to residential and planned unit developments along with, at a minimum, a compliance trigger authority
for hazards to public safety. Also missing are elements related to the five principles for responsible outdoor lighting, including some
over-lighting protections based on lighting standards that are more current than 1998, and very high-angle glare reduction above 80°.
While the Bozeman ordinance is average for its use of metrics and effective requirements; as written, this version would fall short of
achieving DarkSky Recognized status. We encourage Bozeman to consider a stakeholder discussion in an effort to make some
additions/updates to resolve the missing elements and achieve DarkSky recognition.
= Does NOT meet DarkSky requirements
= DarkSky would prefer you meet this requirement but it's not mandatory
DS-MOR-007b
Bozeman
MT
Overview:
The DarkSky Recognized Code program is established by DarkSky International (DarkSky) to recognize government entities or private
developments that adopt ordinances, bylaws, or municipal codes that meet or exceed DarkSky-approved requirements and provisions
for reducing light pollution. Per your application request, submitted through the DarkSky website, DarkSky has conducted a review to
compare your ordinance/bylaw/code against the DarkSky Municipal Code template. This review, shown in detail on page two of this
report, will show adherence and gaps with the submitted ordinance/bylaw/code as compared to the DarkSky Municipal Ordinance
template. This review will give the applicant an understanding of how close the ordinance/bylaw/code is to being DarkSky Recognized.
Review Instructions:
Page two of this review will identify the requirements of the DarkSky Municipal Code template. The document submitted by the
applicant will be reviewed for adherence and/or gaps compared to the template. The results will be indicated for each requirement
with a (Green Y), meaning yes it meets DarkSky criteria, an (Orange N), meaning no it does not meet DarkSky criteria, or a (Yellow P),
meaning the provision would be preferred but is not mandatory. The absence of any orange N would indicate an ability to achieve
DarkSky Recognized status. See legend below:
Review Date: 7/31/2025
Page 1 of 3
DarkSky Recognized Municipal Ordinance Review
Accepted Comments
Y 38.570.010(B) and (F) cite safety and glare concerns
Y 38.570.010€ cites conservation of energy from excessive lighting
Y 38.570.010(C) protects neighbors and the night sky from inappropriate light
P DarkSky would love to see a recital regarding the hazards of artificial light at night on wildlife and
other nocturnal ecosystems, including habitat and crops
P
Some IES standards make illuminance recommendations by lighting zone (e.g., RP43). The Bozeman
ordinance does not mention a community plan for lighting zones. DarkSky recommends
municipalities plan for their nighttime character and a hierarchy of transitions by assigning a lighting
zone overlay or table.
Accepted Comments
N
Street lighting and adjacent public ROW are addressed in the design and construction standards.
However, properties not adjacent to roadway and residential property are not listed within the scope,
and PUD's are exempt from this ordinance and should not be.
Y
38.570.100 is one trigger that forces compliance and 38.570.110 demonstrates the difference
between non-conforming and conforming. It would be nice to see re-zoning or the determination of a
public hazard be included.
Accepted Comments
P There is no specific acknowledgement of federal or state approved lighting, like FAA.
Y Historic and sports lighting have their own set of requirements. Thank you.
Accepted Comments
Y 38.570.040(G)(1), (7), (8), and (10) list prohibitions and does encompass vehicular safety.
Accepted Comments
P 38.570.020(C) does not specifically call for lighting to meet lawful code
N
38.570.040 provides some, but not all outdoor lighting levels found in IES standards. And,
unfortunately, the items listed are from 1998, some of which are excessive by 2022 standards (e.g.,
building entrances at 50 lux instead of RP43's 1 to 30lux range). Additional street lighting
measurement methods have been drafter by Clanton & Associates, are accurate, and listed in the
design and construction guide appendix.
N
Zero uplight luminaires are mandated, thank you. However, newer restrictions above 80° are not
identified specific enough. 38.570.040(G)(4) comes really close, and could meet the DarkSky
requirement by calling for luminaires with G2 rating of 5% emission above 80°.
N We did not see mention of light trespass onto wilderness, habitat, or sensitive land/water.
Y 38.570.040(G)(5) lists values higher than DarkSky's recommendation by a factor of 300%.
Y 38.570.040(G)(3) lists curfew. Thank you.
P We did not see mention of controlled dimming or motion sensing.
N We did not see a CCT limit of 3000K. Very important.
Accepted Comments
N 38.570.050(B)-aiming angle and (C)-trespass help this situation, but do not specifically contain light
to field/bleacher area. The property could be very large.
Y 38.570.050(B) talks about aiming for max candela angle but does not specifically limit emission
above 80°
N We did not see mention of limiting CCT for any lighting, including sports lighting.
Y 38.570.050(C) is an equivalent.
Accepted Comments
Visual Safety
Energy
Sky Quality
Ecosystem Welfare
Lighting Zone Responsibility
New / Replacement Sources
Legal
Light Level
Optic control > 1,000 lumens
Triggers and Amortization
Lawful
Other Exemptions
Habitat Trespass
Residential trespass
Curfew
Controls
Maximum CCT
85% Containment
Bozeman
DS-MOR-007b
Safety Interference
1.2 Purpose
1.3 Applicability
1.4 Exemptions
1.5 Prohibitions
2.0 Lighting Requirements
2.4 Sports Lighting
3.0 Administration
Skyward Light Limit
Appropriate CCT
Intensity Limit
Page 2 of 3
N
The permit process (chapter 1.4.1) and the submittal process (chapter 3.2.6) are documented in the
Bozeman Design and Construction Standards. These processes meet DarkSky expectations for
streetlights, but it would also be expected for any lights within the public right-of-way, institutional
use, commercial developments, and sports fields.
Y Conducted by the city's Engineering Division, the review process is clearly defined in chapter 2.2 of
the Design and Construction standards.
Y 38.570.080 meets the DarkSky requirement with post installation inspections
Y 38.570.090 meets the DarkSky requirement with 30 day remedial action
Accepted Comments
P We did not see any definitions. If needed, DarkSky recommends listing definitions.
Application Process
Review
Enforcement
4.0 Definitions
Overview
Penalty
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