Planning for Dark Skies
For many living in Michigan, Thursday, August 14, 2003 was the day we truly experienced the “inky blackness” of a night without artificial outdoor lighting – as the Great Northeast Power Blackout of 2003 left parts of the northeastern United States in the dark for a day or more.
The Zoning Guru was one of those people who learned that week how much we rely on artificial light at night. We also got a brief glimpse of many stars that we no longer see in the night sky due to light pollution from parking lot lighting and other exterior light sources.
Exterior lighting serves a wide variety of purposes, including:
- attracting attention (advertising),
- aesthetics (such as landscape or architectural lighting),
- safety and security,
- warnings of danger, and
- illuminating our paths.
When overused or poorly shielded, however, such lighting dominates the night sky, blotting out the starts and leaving the characteristically orange glow of light pollution over urban areas.
Can we do anything about light pollution? …absolutely. Do we need to cut the power again? No, but we do need to make smarter and more efficient decisions with regards to our exterior lighting choices if we want to restore the night sky in our urban and suburban neighborhoods.
The overall character and impacts of outdoor lighting in any community is the result of many individual decisions by government, businesses, electric utilities, advertisers and property owners. For these reasons, “dark sky” planning and development of an exterior lighting ordinance are essential steps if you wish to preserve stargazing opportunities or protect rural nighttime character.
Here are some of the questions that should be considered when making decisions regarding exterior lighting:
Where is light needed…and where is it not wanted?
Adequate light should be provided for high traffic areas, including sidewalks, parking lots and building entrances, but check plans carefully to insure that commercial and industrial sites do not cause light trespass problems for neighboring residents and natural areas. Architectural and sign lighting should be carefully aimed to minimize glare, and lamp wattages should be reduced to the minimum needed for visibility.
How much light is needed for a particular site or level of activity?
The human eye is the key factor in determining the proper light intensity for a particular activity. Temporary “night blindness” can be caused by glare from unshielded light sources and extreme contrasts between bright and dark areas of a site. Glare and extreme light/dark contrasts interfere with the eye’s ability to adjust to low light conditions, increasing the potential for accidents.
The design and layout of exterior light fixtures should take into account the need for moderation in light levels and more gradual transitions from bright to dark areas of a site.
Which type of light fixture would be best suited for the task?
Lighting decisions are often based on the lowest cost, rather than the best design. Unfortunately, the cheapest fixture often includes far less efficient optics or reflectors, resulting in the need for higher wattage lamps to provide adequate light. Upgrading to a fixture with higher quality optics can save money over its operational life while reducing energy costs and minimizing light pollution.
For example, a high quality, 250 watt HPS parking lot fixture will provide more illumination over the same area than a similar looking but poor quality 400 watt HPS fixture! Don’t assume that all light fixtures are the same – just as with automobiles there are Lamborghini-like fixtures and ones that are of Yugo-like quality as well!
Contact Building Place Notebook update, including more about ways to effectively regulate exterior lighting, and how to create an exterior lighting ordinance or add detailed lighting standards to your town’s zoning ordinance.
For more information on this topic, contact The Zoning Guru here, or click here to ask about how Building Place can help you effectively regulate exterior lighting, minimize light pollution, and preserve views of the night sky by adding detailed lighting standards to your town’s zoning ordinance.