Urban Sky Glow—the brightening of the night sky over inhabited areas.

Light Trespass—light falling where it is not intended, wanted or needed.

Glare—excessive brightness which causes visual discomfort. High levels of glare can decrease visibility.

Clutter—bright, confusing, and excessive groupings of light sources, commonly found in over-lit urban areas.

 

The proliferation of clutter contributes to urban sky glow, trespass, and glare.