A Note on Illinois Regulations:
We are frequently asked what the "light pollution" or light trespass laws are in the State of Illinois. At present, all regulation of these issues is left up to the local level, excepting in that outdoor lighting is touched upon in some energy efficiency standards that the State enforces; those, however do not directly limit light trespass. This matter is left up to local regulation. The majority of Illinois counties and municipalities do not address these lighting issues at all in regulation; some have some limits set on allowable levels of light trespass onto neighboring properties (see below). At present, the Village of Homer Glen is the only municipality in the state with a really complete outdoor lighting ordinance.
Lighting and light limits are most often mentioned in zoning codes; this is probably the place to start looking in your municipality. Building and development codes are another possibility. But do not be surprised to find that, no matter how disruptive the lights are on your neighbor's property, there may be no law against their operation at any hour of day or night.
Factors which can be Regulated:
Differing amounts of illumination are needed to perform different tasks after dark. For example, the light level needed in a parking area for drivers to safely navigate and see other vehicles, pedestrians and obstructions, is less than is needed to safely fuel vehicles at a gas station. Regulations should list minimum and maximum illumination requirements for common nocturnal activities. The uniformity of illumination can also be addressed; for any nocturnal activity which takes place over an extended area, our visual perception usually suffers if the lighting of the area fluctuates with brighter and darker zones.
Lighting engineers can control the illumination levels while designing an installation by using specifications supplied by light fixture manufacturers. For completed installations, illumination levels can be measured with light meters. Illumination levels are generally measured in foot-candles or lux (see our Lighting Studies > Theory page for more information).
Light Generation per Area
Even with well-designed light fixtures, which put the light they generate into the areas which they are meant to illuminate, there will be light spillage from any illuminated property, just from reflection from illuminated surfaces. To regulate the overall brilliance of a parcel, an effective method is to limit the amount of light generated per net area of land.
One effective method is to specify limits of light generation in lumens per net acre, where the lumens is the total initial output of all the fixtures' lamps on a parcel, and the developable area of the parcel is measured in acres (or fractions thereof). The total initial lumens output of any given lamp is supplied by manufacturers as a matter of standard. This computation is an easy one in the design permit stage for an installation; on existing installations, review of the specific lamps in use will be needed.
Light Fixture Design
The design of the light fixtures used in an installation plays a tremendous part in determining the efficiency and effectiveness of the installation, and the levels of glare and light trespass which it creates. Unfortunately, the U.S. lighting industry currently lacks any uniform set of standards for fixture energy efficiency which can be referred to in legal specification of lighting performance.
Therefore, the best that can be done, when creating legal specifications for allowable and prohibited fixtures, is to clearly define the parameters with which you are concerned. Some may be obvious: The angles, relative to the downward vertical, at which light may be emitted, for instance. Others, such as illumination efficiency per watt of power consumed, or the color quality of the lighting, or the physical appearance of the installation, will require more in-depth definition per the desires of your citizenry. (See our Lighting Studies > Fixtures page for more information.)
Limits to Light Trespass
Light trespass occurs when illumination from one area unintentionally spills into another (often from one parcel of property to adjacent ones). Lighting ordinances should address this important issue; an effective method is to set specific limits to allowable trespass (usually in foot-candles or lux, measured with a calibrated light meter, operated facing in the direction of the neighboring light source, and held at a standard eye level or range of elevations). Trespass level limits should be set particularly low when dealing with spillage into residential areas.
During the design phase of a lighting installation, a lighting engineer should be able to predict and control trespass by careful selection and placement of luminaries; for completed installations, trespass can be measured with light meters, as general lighting levels are (above).
Lighting Schedule Limits
Much common outdoor lighting is an unneeded waste of energy during the majority of nighttime hours. Commercial sign lighting should be extinguished after closing or after a curfew hour; associated building and parking area lighting should also be extinguished or turned down to lower security levels. Many municipalities have curfew periods during the night in their business areas, when businesses are closed, and parking not allowed; even street lighting can be dimmed during that time period. Shutting off or reducing lighting during the 11pm-6am window can reduce the power consumption for nighttime illumination by more than half, and also provide a healthier environment for people who are trying to sleep during that period. Outdoor lighting needs to be controlled by not just a photoelectric switch, but also a time clock (excepting fixtures which are legally designated as needing to be turned on all night).
U.S. citizens who are working to promote responsible outdoor illumination practices find one of the hardest areas to make progress in to be the area of sports field lighting. Playing sports at night requires higher lighting levels over larger areas than any other nocturnal activity. Seemingly, even the long days of summer don't provide enough hours of sunshine to fill our competitive needs; we and our children need to stay out late, and keep playing after night falls.
Unfortunately, besides being brilliant, most sports lighting installations are also very intrusive to the surrounding areas; by and large, the fixtures which are commonly used in these fields and courts achieve bright illumination of the play area while also sending immense amounts of light energy off into the rest of the neighborhood. Also, many play areas end up being illuminated to levels above what is required for safe activity. Lighting companies are often asked by municipalities to determine lighting needs for sports fields; they benefit from selling as many watts of fixtures as they can, and most customers don't have the engineering expertise to critique the proposals which the companies submit.
It is up to your citizenry to decide what level of environmental responsibility needs to be placed on sports lighting in your area, but the subject is not one which should be forgotten while crafting outdoor lighting legislation. Curfews are certainly appropriate, and illumination levels and trespass levels should also be regulated.
Other Factors Which May Be Regulated
- Unsafe and unpleasant glare can occur even when light trespass levels are not exceeded. Regulations can address the issue by prohibiting the lamps of light fixtures from being visible from adjacent areas, either directly or without sufficient diffusion.
- The maximum heights at which lighting fixtures may be mounted can be regulated; generally, the higher a light is mounted, the farther its light will carry. This consideration is especially important in installations close to residential areas.
- Indoor lights which shine outside through windows and doors should be prescribed to follow the same regulations as outdoor-mounted fixtures.
- Do the regulations apply to existing lighting installations, or just to ones put in after the regulations are adopted? If the purpose is to make an overall improvement to the lighting practices in an area, existing fixtures should be required to be brought into conformance within a certain time frame.
- Communities which are concerned about the bad effects of sky glow may want to specifically regulate "up lighting", where fixtures are mounted to shine upwards to illuminate buildings, monuments, signs, etc.
- It is the opinion of our coalition that streetlighting should not be exempt from regulation, especially when it comes to limitations of glare and trespass. Since some streetlighting will be immediately adjacent to (or located on) residential property, trespass levels in those instances may need to be measured from building fronts or other alternative setbacks (rather than property lines). For communities which have some roadways managed by the Illinois Department of Transportation within their boundaries, IDOT's policy is to work with host communities to bring lighting and other factors within the community's standards.