Dusk-to-dawn lighting uses a photocell sensor or an astronomical timer to automatically switch fixtures on as ambient light fades in the evening and off again at sunrise, without requiring manual operation. Most exterior security lighting at apartment communities, HOAs, and commercial properties operates this way rather than on a fixed schedule that would drift with seasonal daylight changes.
On a real property, photocells can fail in an on or off state, be blocked by dirt or spider webs, or be confused by nearby light sources such as a neighboring fixture, causing lights to stay on all day or never trigger at dusk. Photocells mounted where they receive direct light from another fixture at night can also incorrectly stay off.
A light stuck off is more consequential than one stuck on, since the darkened area loses its intended coverage exactly when it's needed most; a stuck-on light mainly wastes energy and shortens fixture life. Neither failure is always obvious during a daytime maintenance walk, since the fixture appears normal when off during the day regardless of whether the photocell works correctly at night.
In a patrol program, officers on night shifts are positioned to notice a stuck-off dusk-to-dawn fixture immediately, and that finding should be reported the same night given how directly it affects visibility along a patrol route or entrance.
Related entries
Official sources
- [1]DOE outdoor lighting guidanceU.S. Department of Energy
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General industry and regulatory usage — not legal advice, and not an endorsement by BSIS, the Department of Consumer Affairs, or any law-enforcement agency. Statutes, regulations, and local ordinances change; verify current text at the official government source or with your attorney.