…continuedBright Lights, Big Problems
While the design of roadway lighting involves common sense and a scientific approach, that logic does not generally apply to retail establishments — especially those that cater to a late-night clientele. “A brightness war has broken out between gas stations throughout America,” observe Peter R. Boyce (Lighting Research Center) and two colleagues in a recent study. They find that if one station installs bright lights, competing stations feel obliged to be brighter still, and as a consequence illumination levels of 1,000 lux (100 foot-candles) — more than double that used in many indoor offices — have become common.
In this environment, retailers who try to hold the line by adhering to IESNA recommended practices perceive themselves to be at a competitive disadvantage. That’s true, for example, of the Home Depot, whose stores have parking lots illuminated at 10 lux (1 foot-candle) on average. But Lowe’s Home Improvement, a rival hardware chain, typically uses exterior lighting five times brighter as part of a campaign to make its stores appear more female friendly.
Lighting engineers now realize that the false daylight from overlit businesses creates unanticipated hazards. Our eyes need time to adapt to different levels of lighting; the more drastic the difference (or the older the person), the more time this adaptation takes. When people leave a brightly lit gas station or fast-food restaurant, their eyes can’t adjust quickly to the sudden darkness out on the street — and they sometimes forget to turn on their vehicle headlights.
In many cases, the brilliant floodlights used to illuminate commercial buildings and parking lots cast their light at such shallow angles that the visual grief from glare may outweigh the potential benefits of illumination. Worst among these are the so-called wallpacks, inexpensive boxlike fixtures on building exteriors that shine most of their light sideways instead of down.
Unfortunately, the terrorist attacks of September 11, 2001, have only fueled the desire for more security lighting. Yet a study recently conducted for the California Energy Commission found that lighting levels have no correlation with a person’s perception of safety. In fact, the energy crisis that brought California to the brink of financial chaos in 2001 has served as a wake-up call to state officials and businesses alike. Spurred by a gubernatorial decree, retail lighting was put under curfew. Many business owners found themselves saving significant sums of money when their existing dusk-to-dawn security lights were equipped with timers or replaced with motion-sensing fixtures.
There is hope yet for starry skies. To date eight states (most recently Massachusetts) have passed laws that restrict outdoor lighting. A growing number of local ordinances have also been approved, though they vary widely in scope. Some require only that new or replacement municipally owned fixtures be full cutoff; others prohibit inefficient mercury-vapor lamps or mandate that all businesses and public buildings turn off unnecessary lighting after 11 p.m. unless they are open to the public. Stricter regulations occur in areas such as Arizona and Southern California, where there are many astronomical observatories. Some local regulations even apply to residential lighting.
Manufacturers and retailers are beginning to recognize the trend in lighting legislation, because in many locales stores must now carry only approved fixtures. New commercial developments now frequently employ full-cutoff lighting for parking lots — and some employ late-night timers — in an effort to keep their energy costs in check.
The overarching problem, explains engineer Benya, is that there are an estimated 10,000 lighting laws in the U.S., which range from “excellent to disaster,” and these existing lighting laws are often challenging to enforce. Moreover, there is no universal set of manufacturing specifications for lighting fixtures. The goal, he says, is to come up with standards, akin to the national codes followed by electrical contractors, that place limits on illumination levels, control levels of glare, and are backed by a common set of scientific standards. One idea gaining acceptance is the concept of tailoring lighting levels locally to one of four environmental zones ranging from “intrinsically dark” to “urban.” A single set of regulations is needed, Benya maintains, because “99 percent of the lighting that’s now installed isn’t designed — it just happens.”