Best Practice Guidance on Security Lights.
Security lighting should provide the minimum level of illumination necessary to light a property.
The designed lighting area may be a site area, building, create a direct visual deterrent to criminals, or it may consist of a presence detection system to switch on when someone invades a selected space.
Poorly designed security lighting may not always act as a real deterrent to crime as glare may cast areas into permanent dark shadow, creating dark spots that may potentially assist intruders. The growing use of sophisticated CCTV security systems may also reduce the need for visible lighting, through the use of infrared lighting and infrared cameras.
The lamps and luminaires range from fixed angle wall-mounted bulkhead units using one 500 lumen lamp to a 20m tower fitted with several 100,000 lumen lamps installed in multi-angle projectors. Maximum lighting levels, usually defined on the ground, would be around 20-30 lux. Ideally, security lights should be controlled by photoelectric switches. For domestic and small scale security lighting, the ILE Guidance Notes recommend passive infra red detectors with a maximum 150W (2000 lumen) tungsten halogen lamp, or low level lighting such as a compact fluorescent porch tube of just 9W (600 lumen).
Light nuisance from domestic security lights can be remedied by relocating the offending light, by readjusting its aim or by fitting a screen to control the spread of light.
a) Control lighting with photo-electric switches on the minimum time-setting — avoid sensors that can be tripped by road or footway users.
b) Timers adjusted to the minimum can reduce the operation of the light
c) A separate switching detector can be used on some models to sense the movement of intruders on the property.
d) Lighting should be directed down and mounted as low as possible to minimize light escape above the property boundary height (such as the hedge or wall) and hence reduce the direct lighting of adjacent premises.
e) Luminaires and detectors should be aimed to detect and light people on the property, not people or animals walking down the street.
f) Balance levels of light with other lighting in and around the site to avoid glare and light spill as well as dark spots.
g) Consider the use of alternative security measures, such as an inside light that is on a time-switch, or CCTV.
h) Minimise the level of illumination as high-powered lights are rarely necessary in domestic situations and can cause glare -usually a maximum of 150W.
i) Lighting can be shielded
j) Special optics or ‘double asymmetric’ luminaries (which are designed to ensure full flow of light over the lit area from each floodlight) can be aimed facing downwards while still spreading light over a wide distance. The reflector becomes less visible to onlookers resulting in low glare to the surrounding locality.
k) Bulkhead or porch lights are cheaper than security lights, use less energy, and have reduced glare. Movement detectors on these lights are generally mounted lower and so are less susceptible to nuisance switching.
l) Vegetation may help screen the light at certain times of year provided the movement of vegetation itself does not trigger light.
m) consider a curfew time of 23.00 after which lighting levels should be further restricted.
The ILE guide is attached as Annex 2.