The Why and How of Light Pollution

Light pollution

Why should a municipality be concerned about light pollution?

Properly designed lighting creates no more light than necessary and puts the light where it is needed to improve human seeing. Badly designed lighting creates extra light that is a waste product and pollutant.

Polluting light interferes with human seeing, is a health hazard for humans and other organisms, is a waste of energy, and ruins our view of one of the great natural wonders – the night sky.

What a can a municipality do to minimize light pollution?

Establish reasonable requirements for lighting installations. (

Require a ‘lighting plan’ for all new lighting installations. Computer programs exist that can predict light levels based on the physical plan and type of fixtures.

Require ‘full cutoff’ light fixtures that direct the light where it is useful for seeing.

Minimize glare by eliminating direct view of light sources (e.g., require alternatives to ‘wall pack’ fixtures).

Institute a curfew on commercial lighting so that commercial premises and signs are not illuminated when there is no one to see them.

Set reasonable light levels for street lighting. Use dimmable light fixtures so that street lighting levels can be reduced, especially at late hours.

Set reasonable maximum allowed light levels for other facilities, such as plazas, parking lots, gas stations, and car dealerships.

Designate certain park areas as ‘dark sky friendly’ by careful control over light levels and glare.

Establish limits on light trespass so that the glare (luminance) or light level (illuminance) from an adjacent source cannot have an effect on private property.

Establish a program to measure and document light levels (both luminance and illuminance) throughout the municipality.

Lighting without an observer is completely ineffective. Require security lighting to be motion activated and accompanied by human or video surveillance.

Peter Hiscocks

Chair, Subcommittee on Light Pollution, Royal Astronomical Society


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