Cost savings from lower energy use and elimination of traditional lighting maintenance typically provide a financial ROI of three to five years, with some case studies even showing a one-year return. Case study information is available from leading manufacturers.
Figure 3 illustrates the reduced Total Cost of Ownership picture for LED lighting fixtures compared to high intensity discharge lighting typically used for large area illumination.
Improving Visual Acuity
Visual acuity is the ability to discern details at a certain viewing distance. In general, the brighter and more even the lighting, the better the visual acuity is for a given observer. When there are light and dark spots in the area being viewed, visual acuity is diminished across the scene. Lighting uniformity and good scene color are factors that improve visual acuity and provide pedestrians with a more comfortable environment because they can see better than in traditionally lighted areas. This is also important, of course, for patrolling officers and first responders.
The lower TCO of LED lighting compared to traditional outdoor lighting and the variety of fixtures available make it feasible to design much more uniform area lighting and pathway lighting. The white light quality of LEDs also improves the color aspect of lighted areas.
Safety and Security Design Considerations
It has long been known that good lighting is an effective crime deterrent; thus, lighting is one element in CPTED (crime prevention through environmental design). Landscaping is part of the lighting picture, as trees, shrubs and other greenery can block light and create shadows and hiding places. In most cases, it is not desirable to simply eliminate such greenery; however, a combination of trimming and additional LED lighting can make potential nighttime hiding places very unattractive.
Small motion-activated LED lighting fixtures in such locations are a considerable deterrent — they provide a bright indicator light signaling when someone is present, and thus can deter unwanted or prohibited behavior that would otherwise go unnoticed.
Many models of outdoor LED fixtures and LED lighting intended for video surveillance applications incorporate a light sensor element and have inputs enabling motion-activated or scheduled control.
There are many factors prompting the growing adoption of lighting ordinances, the primary one being public safety. LED lighting makes it easier to comply with these ordinances because LED is more highly directional than traditional lighting, and because the fixtures are designed for compliance to common ordinance requirements.
A good general summary of the concepts and implementation of municipal lighting regulation is the Outdoor Lighting Code Handbook published by the International Dark-sky Association (IDA) in 2000 and revised in 2002 (www.darkskysociety.org/handouts/idacodehandbook.pdf). More recently, the Illuminating Engineering Society of North America (IESNA) and the IDA collaborated to produce the Model Lighting Ordinance (MLO), which was released in mid-2011. (www.darksky.org/outdoorlighting/mlo.)
The MLO offers several innovations to outdoor lighting regulation, including the use of five lighting zones to classify land use, with appropriate lighting levels for each. Other innovations limit the amount of light used for each property and regulate the amount of uplight (skyward-directed lighting) for street lighting.
Video Network Bandwidth Reduction
Of particular importance to both security departments and IT security, LED lighting can reduce the bandwidth requirements of video streams from low-light areas.
Nighttime video from outdoor network cameras and network-encoded analog cameras have a lower compression rate than daytime video from the same cameras. The same is true for cameras in indoor areas that have a lower level of lighting after hours. In order to improve the low light image, cameras amplify the video signal—which has the effect of amplifying the electronic noise (which appears in the video image as randomly changing patterns of tiny dots). The amplification factor, called gain, is the extent to which the amplifier boosts the signal.