Light pollution from excess articial light causes problems for people and wildlife. Sometimes we cannot even see the stars because of unnecessary artificial lights shining upward.
Good Neighbor Outdoor Lighting
How, you might ask, could "outdoor lighting" be a subject on a site devoted to environmental concerns? Well, consider that half our environment is night time, and for millennia, humans have become well adapted to (and actually dependent on) darkness. In less than one hundred years, use of artificial lighting has become widespread. Although artificial lighting has been a benefit for moving about safely at night, it can also easily and inadvertently become obtrusive to our neighbors and others-light does not stop at property boundaries.
What are Glare, Light Trespass and Sky Glow?
Glare is the direct view of light source against dark background. Glare overloads our eyes and actually reduces our ability to see in a generally dark environment, which can cause accidents. The cause of glare is poorly shielded lights that are aimed at least partially horizontally, not down onto the pavement.
Light Trespass is unwelcome light spilling off originating property. As with glare, the causes are, first, poorly shielded lights which are aimed partially horizontally, not down, and secondly, too much light power used for the application.
Sky Glow is a general brightening of the normally black night sky caused by artificial light pollution. Excessive sky glow can almost completely block out views of stars. The main causes are upward-directed light (again from poorly shielded fixtures) and too much light power used for the application.
Effects of Artificial Light
General use of artificial lighting, which began about 100 years ago, has been accelerating in the past 50 years, and if unchecked will completely block out any natural-sky views in the not-too-distant future.
This picture shows the view from space of upward directed light. The views of the mid-70's and 1997 are from satellite data; the late '50's and 2025 views are extrapolations from the satellite views, using known or expected amounts of outdoor lighting. All the light that is visible from space is obviously wasted energy which produces no useful effect (and lots of bad effects) for people on the ground. (Picture credit Fabio Falchi, The Light Pollution Science and Technology Institute [Istituto di Scienza e Tecnologia dell'Inquinamento Luminoso] www.istil.eu and CieloBuio, the organization that promotes the adoption of several of the best laws against light pollution: www.cielobuio.org)
Outdoor lighting is growing at greater than 5% per year. At the present time, artificial lighting obscures the Milky Way (our home galaxy) from view of more than 70% of the households in the United States. In a dark-sky site, about 2500 stars are visible; but in the sky over a large city like Boston, that number is reduced to less than 100.
What can we personally do about this? Use Fully Shielded light fixtures, use the proper amount of light for the job (resist the urge to over-light), and turn off light (either manually or with motion sensors) when there is no one around to use it. Advocate to others how these simple steps will result in both reduction of light pollution and conservation of energy. Demand that your cities and towns also follow these principles.
Principles of Good Neighbor Outdoor Lighting
We all like the freedom to do as we want on our own property. However, at the same time most of us realize it's also important not to intrude on our neighbor's rights by our actions. We would never think of either making very loud noises that would disturb our neighbors or of aiming our water sprinkler so it sprays on their house or of letting our dog exercise on their lawn. But often we don't stop to think that the outside lights we install on our house can be just as obtrusive to our neighbors.
The fact is that the light our fixtures produce doesn't stop at our property boundary. Light travels in straight lines from our outside fixture and can directly shine in our neighbor's windows or on his property, and then it becomes obtrusive and unwelcome. A bright, lighted, unshielded bulb on our house or yard will cause unpleasant glare in our neighbor's eyes. Glare is the uncomfortable situation in which the human eye is unable to respond both to the dark surround and also a very bright source. We instinctively squint our eyes to try to close out the offending light. If our light trespasses through the windows of our neighbors' house, and into, for example, their bedroom, then our light can even affect their ability (and right) to have a sound sleep.
The solution to prevent glare and the majority of light trespass is very simple and inexpensive. We can apply shielding to our bright outside lights, such as floodlights and other bare bulbs that are bright. "Bright" is defined In Acton's outdoor lighting bylaw as 120 watts for incandescent bulbs and 20 watts for fluorescent bulbs. Even though Acton's Outdoor Lighting Bylaw does not apply to single family dwellings we residents are on our honor to do the right thing in regard to our neighbor!
Shielding is used to block the lamp's rays from traveling upward (causing sky glow) or sideways (and off your property–potentially causing a nuisance to your neighbor). To direct the lamp's rays onto the ground–the place we are trying to illuminate after all–the shield should cover the top and sides of the lamp. The bottom–the only open side of the fixture–is parallel to the ground. If we view the fixture from a point horizontal to the lowest point of its shield, we will not see any direct light from the fixture. The only visible light should be that illuminating the ground–where of course it is the place where it is needed! A fixture like this -shielded on the top and sides with a flat horizontal opening on the bottom–is called Fully Shielded. An example of a Fully Shielded fixture for residential use (with the brand name Glare Buster) is shown here.
One light that is commonly used on many houses to light driveways and yards is the Parabolic Reflector (PAR) lamp. This is the familiar cone-shaped bulb about six inches in diameter. If unshielded, it can project light for long distances, because of the focusing reflector built into it.
The picture on the right shows a close-up of the light with shield attached. Quiz question—is this a Fully Shielded fixture? (Answer: Yes) Picture credit Bern Kosicki.
You can learn much more about shielding and principles of good lighting from sites sponsored by the New England Light Pollution Advisory Group (NELPAG) and the International Dark Sky Association (IDA). We recommend all these sites to you.
Bright Lights in Your Eyes? A Survival Primer for Acton Residents
Acton has an Outdoor Lighting Bylaw that affects primarily commercial developments. Any commercial development after 2004 that requires a Site Plan Special Permit (developments that are above a certain size need this permit) must comply with the 2004 Acton Outdoor Lighting Bylaw. (See Section 10.6 of the Zoning Bylaws http://www.acton-ma.gov/index.aspx?nid=167.) Site Plan Special Permit developments that were permitted between 1984 and 2004 must follow the previous 1984 Acton Outdoor Lighting Bylaw.
If you believe that the offending commercial development falls into one of these categories, then you should call the Acton Zoning Enforcement Officer, Scott Mutch (978) 264-9612 (Planning Department) and state your case.
Various Acton Boards of Selectmen have agreed that the Town should also follow the outdoor lighting bylaw (but there is no binding agreement that requires them to do so).
For issues with lights that are owned by the municipal government (library, streetlights, South Acton Train Station parking lot, transfer station, police and fire departments), call the Municipal Properties Director, Dean Charter (978) 264-9629.
For problems associated with any school-owned property, call the Coordinator of Facilities and Transportation, John D. Head; (978) 264-4700.
Acton's bylaws don't cover residential lighting. However, often times a simple discussion with the owner can solve the problem. Here are some tips on how to approach that discussion, abstracted from an excellent International Dark Sky information sheet (http://docs.darksky.org/PG/PG3-residential-lighting.pdf):
We encourage you to read the entire IDA document that these tips were borrowed from. If you need for more help, write to email@example.com and we'll try to provide support to you.
1984 Acton Outdoor Lighting Bylaw
The purpose of Acton's 1984 Outdoor Lighting Bylaw is to control glare by requiring bright lights to be aimed down, and also to control light trespass from the originating property onto an adjacent property by additional shielding.
This bylaw is strict in terms of requiring effective shielding. However, OLEC found the following shortcomings in this bylaw:
Technical requirements for shielded lights; the current bylaw requires a strongly shielded light, but doesn't use modern terminology.