Outdoor Lighting For Safety And Security Is A Complicated Matter
At first glance, exterior lighting might seem a simple matter of providing enough light so that people can see each other, and spot hazards in their paths — and when in doubt, err on the side of more light. But in reality, outdoor lighting is a complicated matter.
Consider a phrase that often defines the goal of exterior lighting: safety and security. While the two go hand in hand, they are not the same. Safety issues are related to tripping and falling, says David Aggleton, president of Aggleton & Associates Security Consultants, and for this reason "exterior lights in a parking lot are usually pointing down on a horizontal surface so that you can see a shiny patch of ice or a pothole." Security is associated with seeing the face or body of a potentially threatening person, so "instead of vertical light you need horizontal light that will reflect off a vertical surface," Aggleton explains.
So safety and security have two different requirements, and you can't cover both without compromising, Aggleton says. "The compromise is to have light that shines down and spreads out to give you both," he notes. It's important to select the right light fixture that will create a spread of light.
According to Eric Richman, senior research engineer at Pacific Northwest National Laboratory, Richland, Wash., the conventional wisdom is that more light is better, but from a security standpoint, too much of the wrong kind of light, aimed in the wrong direction, can cause glare. Moreover, security camera function depends on various lighting factors including uniformity/contrast, light color, and intensity. No one type of lighting will be best in all situations, he says.
Striking A Balance
"From a safety perspective, too little light can provide an opportunity for a criminal to take advantage of a consumer," says Mike Ross, vice chair of the Security Lighting Committee of the Illuminating Engineering Society of North America (IESNA) and president of GMR. "On the other hand, too much light as a result of a poor lighting application can create glare and blind spots, resulting in potential risks to patrons. Too much or too little improperly directed lighting affects security cameras and impacts the clarity of images from those cameras." Ross also notes that poor lighting can have a negative effect on a brand or on business activity.
Richman also notes that companies often bypass The Lighting Handbook from IESNA when determining lighting requirements and go straight to the G-1-03 guidelines, because they are worried about litigation. But the G-1-03 guidelines should be used only "where there is a specific security issue or if you are in a high crime neighborhood," Richman says. "A lot of people may go to the G-1 first, but you may be wasting light."