the hours of darkness with overlapping cones of light. The two primary
methods of using continuous lighting are glare projection and controlled
Glare Lighting. Glare lighting uses luminaires slightly
inside a security perimeter and directed outward. It is considered a
deterrent to a potential intruder because it makes it difficult for him to
see inside the area being protected. It also protects the guard by keeping
him in comparative darkness and enabling him to observe intruders at
considerable distance beyond the perimeter.
Controlled Lighting. Controlled lighting is used when it is
necessary to limit the width of the lighted strip outside the perimeter
because of adjoining property or nearby highways, railroads, navigable
waters, or airports. In controlled lighting, the width of the lighted strip
is controlled and adjusted to fit a particular need, such as illumination of
a wide strip inside a fence and a narrow strip outside, or floodlighting a
wall or roof. Unfortunately, this method of lighting often illuminates or
silhouettes security personnel as they patrol their routes. Controlled
lighting may provide direct or indirect illumination.
a) Direct Illumination. This lighting concept involves
directing light down to the ground. Its goal is to provide a specified
intensity of illumination on intruders, facilitating their detection by CCTV
or security patrols.
b) Indirect Illumination. An alternative lighting concept
involves backlighting the intruders against a facility. This may be done by
placing lighting away from the building and directing it back toward the
walls so shadows will be cast on the building by the threat. Such
applications are most effective if the luminaires themselves are near ground
level. This indirect concept is also aesthetically pleasing, illuminating
the architecture during darkness.
Standby Lighting. A standby lighting system is different from
continuous lighting since its intent is to create an impression of activity.
The luminaires are not continuously lighted but are either automatically or
manually turned on intermittently or responsively when activity is detected
or suspected by the security force or IDS. Lamps with short restrike times
are essential if this technique is chosen. This technique may offer
significant deterrent value while also offering economy in power consumption.
Intermittent Lighting. A lighting system can be developed to
turn lights on at random times as a deterrent to some threats. It can use
either direct or indirect illumination concepts. While an intermittent
lighting system can involve a duty cycle of 10 to 50 percent, it may increase
operational and maintenance costs, it may force the use of inefficient lamps,
or reduce lamp life. Deterrence can actually be higher for such a system