Exterior lighting can and does provide security – protecting people from assault or injury while arriving and departing from a facility after dark and making it difficult for an intruder to approach the facility without fear of being observed.

Some basic precepts of exterior security lighting:

• Positioning – Parking lot and sidewalk lights should avoid producing shadows cast by trees and tall shrubs.
• Direction – Lights fixed to buildings should be set at a roughly 45-60 degree angle from the building so as to project their light as far out from the building as possible without becoming obtrusive to neighbors or creating a direct glare into the eyes of people approaching the building on foot or in a vehicle.
• Color Rendering Index – If a closed circuit TV (CCTV) system is being used, it is important to consider the color rendering index (CRI) when selecting a type of exterior lighting. High-pressure sodium lights, favored for their lighting efficiency, are not favored by CCTV systems. This type of lighting does not meet the quality lighting color rendering index (somewhere in the range of 22-65) to faithfully render clothing colors and facial features. Metal halide lighting (with a range of 65-85) or fluorescents (52-92) do meet those standards. Mercury vapor lights have a CRI of about 50. This could be a critical difference in an identification process. The objective is to achieve the highest CRI possible for the benefit of the CCTV system. However, there are trade-offs. Metal halide lighting is not very energy-efficient when compared to fluorescent lighting. On the other hand, fluorescents are not very light-efficient in cold weather due to a drop-off in lumens, in addition to which, the longer tubes of a fluorescent lamp require larger lighting fixtures.
• Heat-Sensitive Cameras – If heat-sensitive or infrared television cameras are employed, no lighting of any sort will be used. Infrared cameras view only in shades of a single color, usually gray or a soft green.

For more on building security measures, check out Building Security: Strategies & Costs by David Owen published by RSMeans.