Reclaiming the Night: Urban Light Pollution, Solutions, and Open Data
NYC Open Data Week – March 25, 2026
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Speaker: Ruoyu Li - Graduate Student, NYU Center for Urban Science + Progress (CUSP); Graduate Research Assistant, NYU Light Pollution Project; DarkSky International Advocate
Moderator: Michael Xie - NYC Open Data, NYC OTI
Introduction and Personal Background
Ruoyu Li introduces himself as a graduate student at NYU’s Center for Urban Science and Progress (CUSP), a graduate research assistant on a light pollution project, and an advocate with DarkSky International. He explains that he has worked on light pollution advocacy for more than a decade through presentations, public outreach, research, and community organizing.
He also discusses his involvement with:
ASPRS NYU Student Chapter
DarkSky International
DarkSky New York
International advocacy efforts in both New York and Beijing
He explains that DarkSky International’s mission is to protect communities and ecosystems from harmful effects of light pollution through:
Outreach
Advocacy
Conservation
Better lighting design
Recent New York State Light Pollution Legislation
Li begins by discussing recent media attention surrounding proposed New York State legislation on outdoor lighting.
He explains that many headlines inaccurately described the proposal as requiring lights to be turned off after 11 p.m., while the actual bill:
Allows essential lighting
Encourages proper shielding
Supports timers and motion sensors
Focuses on responsible lighting rather than total darkness
He identifies two companion bills:
Assembly Bill A4615
Senate Bill S5007
Participants are encouraged to:
Check whether their representatives sponsor the bills
Contact legislators
Advocate for stronger support
Li emphasizes that public awareness is currently one of the most important aspects of light pollution advocacy.
Global Examples of Light Pollution Regulation
The presentation expands beyond New York to discuss legislation and regulation elsewhere.
Examples include:
Puerto Rico’s dedicated light pollution law (2008, later revised)
European environmental regulations
China’s newly approved Ecological and Environmental Code
Li highlights Puerto Rico as a particularly important case because it combines:
Legal regulation
Wildlife protection
Community advocacy
One example involves sea turtle conservation, where beaches use red lighting to avoid disorienting hatchlings that would otherwise move toward bright roads and urban lighting instead of the ocean.
Another Puerto Rico example describes a local advocate successfully convincing officials to remove harmful lighting near a lighthouse that had previously destroyed dark-sky viewing conditions.
Defining Light Pollution
Using DarkSky International’s definition, Li explains light pollution as:
“human-made alteration of outdoor light levels from those occurring naturally.”
He distinguishes between:
Necessary lighting for safety and function
Excessive or wasted lighting
He cites research estimating:
Light pollution increasing roughly 10% annually
80% of the global population living under sky glow
99% of people in the U.S. and Europe unable to see the Milky Way
Types of Light Pollution
Li outlines major forms of light pollution:
Glare
Light trespass
Sky glow
Examples include:
Blinding vehicle headlights
Billboards
Neighboring lights shining into homes
Urban sky glow reflecting off clouds and water
He contrasts heavily light-polluted cities with Flagstaff, Arizona, which adopted early dark-sky regulations because of its astronomical observatory.
Flagstaff is presented as evidence that:
Economic growth does not require severe light pollution
Legislation and proper lighting design can significantly reduce sky glow
Additional examples include:
Fishing boats using powerful lights
Daytime glare from reflective buildings
Bird collisions caused by glass facades
Lighting, Safety, and Public Housing
Li challenges the idea that brighter lighting automatically improves safety.
Using visual comparisons, he argues that:
Poorly designed lighting can blind observers
Excessive brightness can hide potential threats
Shielded lighting often improves visibility
He discusses controversial floodlight experiments conducted in New York public housing developments, where researchers claimed brighter lighting reduced crime.
Li argues that:
The conclusions are debatable
Residents often disliked the lighting
The issue raises concerns about environmental equity
He contrasts wealthier communities, where residents often influence lighting decisions, with public housing residents who may have little control over lighting conditions.
Ecological Impacts
A substantial portion of the session focuses on ecological consequences.
Topics include:
Sea turtle disorientation
Bird migration disruption
Insect decline
Fish and marine ecosystem disruption
Impacts on bats and nocturnal wildlife
Li explains that New York lies on a major migratory bird corridor and cites estimates that approximately one billion birds annually die from building collisions.
He discusses the “Tribute in Light” memorial in New York City as a well-known example where birds become trapped in powerful light beams. Volunteers now monitor migration conditions and temporarily shut off the lights when large numbers of birds become trapped.
The presentation also discusses effects on:
Plant growth cycles
Seasonal timing
Agricultural systems
Examples include trees and crops showing altered growth patterns near artificial lighting.
Human Health and Circadian Rhythms
Li explains that human biology evolved around natural cycles of darkness and light.
He discusses:
Melatonin disruption
Sleep disturbance
Blue light exposure
Possible links to disease and cancer risk
Examples include:
LED lighting with strong blue wavelength peaks
Phones and computer screens
Night mode features designed to reduce blue light exposure
He contrasts:
Bright blue-rich daylight conditions
withWarmer amber lighting more appropriate for nighttime environments
Responsible Lighting Principles
The presentation introduces DarkSky International’s “Five Principles for Responsible Outdoor Lighting.”
Key concepts include:
Use light only when necessary
Direct light only where needed
Use the lowest effective brightness
Control lighting with timers and sensors
Prefer warmer color temperatures
Li shows examples of:
Shielded residential lighting
Well-designed sports field lighting
Poorly shielded park and city lighting
He repeatedly emphasizes:
“More light does not mean more safety.”
Equity and the Dark Sky Movement
Li argues that dark sky preservation should not become a privilege only available to wealthier communities.
He discusses international dark sky designations and notes that:
Many are located in wealthier regions
Major cities are increasingly showing interest in dark-sky initiatives
A notable example is Shenzhen, China, becoming an International Dark Sky Community despite being a dense megacity.
Li argues that awareness should be incorporated during periods of rapid urbanization so that cities avoid expensive retroactive corrections later.
New York City Examples
The presentation includes several local examples of excessive or poorly managed lighting:
Parking lot lighting left on overnight
Reflections from new skyscrapers
Decorative building lighting
Floodlighting in parks
He specifically discusses:
The new JPMorgan building
Con Edison parking lot lighting
Lighting in Central Park
Li also reviews existing NYC legislation passed in 2018 regulating:
Lighting in city-owned buildings
Bird migration protections during peak migration periods
He notes that many previous state and city bills addressing light pollution have failed or stalled despite repeated reintroduction.
Open Data and Light Pollution Research
The final section focuses on measurement and open data.
Li discusses NYC 311 complaint data related to:
Parking lot glare
Excessively bright signs
Street lighting complaints
He demonstrates how NYC Open Data allows researchers to map complaint locations and identify recurring issues.
He also highlights publicly available tools and datasets including:
Light Pollution Map
VIIRS satellite data
NASA Black Marble
Google Earth Engine datasets
Colorado School of Mines nighttime light composites
DMSP historical satellite imagery
SDGSAT-1 satellite imagery
Applications discussed include:
Disaster recovery analysis
Energy studies
War monitoring
Long-term urbanization analysis
Li explains that newer satellites such as SDGSAT-1 provide:
Higher spatial resolution
Multiple spectral bands
Better visibility of blue wavelengths
Citizen Science and Community Participation
Audience discussion includes community science initiatives such as Globe at Night.
Participants can:
Observe constellations
Compare visibility conditions
Submit observations online
Li explains that citizen science datasets have already been used in published research estimating annual increases in global light pollution.
Audience Questions
Questions address:
Construction lighting
Air pollution interactions
Citizen science
Blue wavelength impacts
Open datasets desired from NYC agencies
Li says one dataset he would particularly like released publicly is a detailed inventory of NYC streetlights, including:
Locations
Fixture types
Installation dates
Lighting designs
He notes that DOT declined requests for some of this information due to stated security concerns.
Conclusion
Li concludes by emphasizing that light pollution should be treated as an environmental pollution issue similar to:
Air pollution
Noise pollution
He argues that solutions already exist through:
Better design
Responsible use
Regulation
Public awareness
Open data
Community advocacy
The session closes with encouragement for participants to:
Support legislation
Join advocacy organizations
Conduct research
Promote responsible lighting practices
Use open data tools to study and visualize light pollution impacts.
RESOURCES
DarkSky International — the advocacy organization whose mission and dark sky place certification program Ruoyu Li presented
NYU Center for Urban Science + Progress (CUSP) — the urban data science graduate center where the speaker is a graduate student and research assistant
Five Principles for Responsible Outdoor Lighting — the DarkSky–IES framework for useful, targeted, low-level, controlled, warm-colored lighting
DarkSky Outdoor Lighting Code Templates — free legal and technical ordinance templates advocates can send to local representatives
NASA Black Marble — VIIRS-derived nighttime lights product suite used to study energy, disasters, and light pollution
Earth Observation Group VIIRS Nighttime Lights — annual composite nighttime light data from the Colorado School of Mines
Globe at Night — international citizen science program for measuring and submitting night sky brightness observations
Light Pollution Map — interactive map with layered VIIRS satellite and sky brightness data discussed as a public-friendly visualization tool
NYC 311 Service Requests dataset — NYC Open Data source for parking lot glare and streetlight complaints from 2020 to present
NYS Assembly Bill A4615 — proposed New York State light pollution legislation (identical companion to Senate Bill S5007)