Step into the zone: How Lighting Zones promote better urban design

Image credit: Helge Klaus Rieder / public domain
1264 words / 5-minute read

Regular readers of the blog know that light pollution is a growing problem around the world. Each year, nights get brighter as humans deploy ever more outdoor lighting. This makes it harder to see the stars at night. It can also harm wildlife, threaten human health, and diminish the natural nighttime environment.

We know that much of this problem comes from wasted light. Lights are often too bright, shine where they are not needed, or stay on when they are not useful to users of outdoor spaces. Of course, this does not mean all outdoor lighting is bad. Lighting is important for safety, work, and amenity in public spaces. The challenge is using the right amount of light in the right places and at the right times.

Public policies can help reduce light pollution, but only if people support them. Many people want darker skies, but they also want safe streets, active businesses, and control over their own property. Any workable solution must balance these needs.

​One possible solution is the use of Lighting Zones. Lighting Zones guide limits on outdoor lighting based on the type of activity on a property and expectations for the availability of light at night. Different places have different lighting needs, and Lighting Zones try to match lighting levels to those needs. This month, we explore how Lighting Zones came to be, what their benefits and drawbacks are, and what new developments in this area mean for urban planning.

A New Twist On An Old Idea

Lighting Zones emerged from ideas long used in city planning. Cities often divide land into zones, such as residential, commercial, or industrial areas. An overlay zone adds extra rules to these areas without changing the original zoning. The intent of land-use planning is to promote desirable development outcomes as well as more efficient uses of resources.

The idea is to match allowable activities on land parcels to their geographic situation. Compatible uses tend to cluster together. Zoning tends to isolate and restrict activities the public finds objectionable. In short, planners believe that zoning influences patterns of human behavior. Furthermore, the resulting changes are beneficial to society.

A map of lighting zone overlays for the City of Flagstaff, Arizona. The lower allowances in Lighting Zone 1 (left) are meant to protect the nearby U.S. Naval Observatory-Flagstaff Station.

As applied to outdoor lighting, each Lighting Zone has its own rules for new buildings and outdoor spaces. City planners can then check if a new project follows the rules for its zone. This approach allows cities to focus on lighting without rewriting their planning laws.

But zoning rules can be hard to design and use correctly. Also, many urban planners don't learn about outdoor lighting in their formal education. They often know little about lighting technical information. As a result, outdoor lighting policies like ordinances and bylaws can be ineffective.

​The creation of Lighting Zones intended to make lighting rules easier to understand and apply. The idea originated from international standards promoted by the International Commission on Illumination, known by the French abbreviation "CIE". The Environmental Zones first appeared in a 2003 CIE publication intended to reduce obtrusive light at night. In 2011, these ideas were later expanded in the Model Lighting Ordinance (MLO). The result offered local governments a clear way to regulate outdoor lighting.

What the Lighting Zones Are

Lighting Zones are divided into five levels, from Zone 0 to Zone 4. These cover a wide variety of situations from areas with little or no outdoor lighting to very bright places, such as busy city centers or entertainment areas like the Las Vegas Strip. The table below shows the definitions of the Lighting Zones and how they relate to the CIE Environmental Zones.

Lighting Zone	Definition	Equivalent CIE 150 Environmental Zone	Examples
LZ0: No ambient lighting	"Areas where the natural environment will be seriously and adversely affected by lighting"	E0 ("Intrinsically Dark")	Astronomical observatories; Starlight Reserves; International Dark Sky Reserves and Sanctuaries
LZ1: Low ambient lighting	"Areas where lighting might adversely affect flora and fauna or disturb the character of the area"	E1 ("Dark")	Relatively uninhabited rural areas; national parks and landscapes
LZ2: Moderate ambient lighting	"Areas of human activity where the vision of human residents and users is adapted to moderate light levels"	E2 ("Low District Brightness")	Sparsely inhabited rural areas; villages or relatively dark outer suburban locations
LZ3: Moderately high ambient lighting	"Areas of human activity where the vision of human residents and users is adapted to moderately high light levels"	E3 ("Medium District Brightness")	Moderate-density rural and urban settlements; small town centers of suburban locations
LZ4: High ambient lighting	"Areas of human activity where the vision of human residents and users is adapted to high light levels"	E4 ("High District Brightness")	The most intensely developed city centers with high levels of night-time activity

Lighting allowances tend to scale up as the Lighting Zone number increases. The goal is simple: allow more light where people expect it, and less light where darkness is important. This system helps planners and decision makers set clear limits. Instead of arguing about every new light proposed, they can use the zone rules to guide their choices.

Pros and Cons of Lighting Zones

Lighting Zones have several benefits. They are flexible, easy to explain and match well with existing land-use zones. In some cases, local governments map them to their existing zoning systems. Lighting Zones help communities set clear lighting expectations for different areas. They can mediate dispute resolution as land uses change over time. And they are a tool local governments can use to push back against requests for exceptions or adjustments to development rules.

But there are also some drawbacks. Some places do not fit neatly into one zone. If zones are applied carelessly, areas may be given higher lighting limits than they really need. Over time, this can lead to brighter nights instead of darker ones. Some people also worry that Lighting Zones are too simple and do not capture real-world needs. Others may resist them because they do not want new rules or limits on outdoor lighting.

Many communities do not make use of Lighting Zones in their planning systems. At some level this is because of a lack of awareness that they exist. But even when planners know about Lighting Zones, they may hesitate to embrace them. They may find the distinctions between Lighting Zones unclear. In turn, they find it difficult to know when and where to apply them. Elected officials sometimes turn away from adopting policies they don't completely understand. They may also sense a lack of public support for this kind of zoning. 

Updates to Lighting Zones in 2026

The Illuminating Engineering Society, a U.S.-based professional organization of lighting engineers, promotes various lighting recommendations. Among its 'recommended practices' is RP-43 ("Lighting Exterior Applications"). 2026 will see a major update to this document. It's relevant to this discussion because RP-43 maintains the Lighting Zone definitions that first appeared in the MLO.

While the new recommendations are not yet published, they are public by way of the American National Standards Institute (ANSI) review process. We know that they contain a few amendments to the Lighting Zones. One major change is the addition of a Natural Conditions Zone. At last, this recognizes that the goal in some places should be to keep them naturally dark. These are places where the human presence at night is small or nonexistent. As a result, there is no expectation of permanently installed outdoor lighting. Where lighting deemed necessary, it should take the form of flashlights/torches and similar portable lighting.

​This is a turning point for the lighting engineering and design community. Before this update, the zone with the most restrictions was Lighting Zone 0. The definition of that zone calls for "little or no lighting" but does not exclude lighting altogether. Establishing the Natural Conditions Zone acknowledges that some situations call for a total prohibition of permanent outdoor lighting installations. As a result, the new RP-43 brings clarity to the Lighting Zone 0 definition. While Lighting Zone 0 still allows the installation of permanent lighting, its use is minimized by design. These updates help protect places where darkness is especially important, while still allowing bright lighting where it is legitimately needed.

Looking Ahead

Lighting Zones are a useful tool for managing outdoor lighting. When used carefully, they help protect dark skies while keeping places safe and usable at night. But for Lighting Zones to work well, they must be applied thoughtfully and supported by the public. As lighting technology and community needs change, the zones and their rules will also need to change. Right now, the biggest challenges are that many people do not know about Lighting Zones, and some resist new regulations. Better education and clear communication can help show that smart lighting benefits everyone.