02.10.15 Outdoor Lighting: Visibility, Liability, and the Future

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By 2020, predicts the U.S. Department of Energy, 75% of the United States’ outdoor lighting will use light-emitting-diode (LED) technology. This conversion from high-intensity discharge (HID) and other legacy-lighting sources represents an unprecedented opportunity to improve the quality of the outdoor-lighted environment while saving energy. But, says a panel of three outdoor-lighting experts assembled by the National Lighting Bureau, if the only focus is energy efficiency, it’s possible that the quality of 2020’s outdoor lighting will be inferior to what we have today. The panel was one of four the Bureau hosted as part of its annual lighting forum sponsored by the Edison Report and moderated by Edison Report Publisher Randy Reed.

One of the outdoor-lighting experts – Bob Parks, L.C., executive director of the Smart Outdoor Lighting Alliance – referred to new research showing that some outdoor lighting provides better nighttime visibility when it is not uniform, because uniformity reduces the contrast that is an essential element of good visibility. Mr. Parks said the same research also showed that illumination levels could be reduced by as much as half the contemporary recommendations, with no reduction in visibility, when the illumination is provided by broad-spectrum, white-light sources, like some LEDs. Mr. Parks opined that contemporary standards are out of date because they specify illumination levels and uniformity that are too high for broad-spectrum white light. Nonetheless, because complying with standards is a shield against lawsuits alleging that lighting was inadequate and therefore caused or contributed to an accident, those who own or operate outdoor-lighting systems conform to standards. As an example, Mr. Parks pointed out that the New York City Department of Transportation will replace some 250,000 conventional street- and highway-lighting units with LED units over the next two years. When it does, however, the new lighting will comply with existing standards that do not consider the specific attributes of LED lighting. As a result, the new lighting may actually provide less visibility and save less energy than it otherwise could, and it will probably produce more glare.

The slow process of developing standards and regulations was acceptable before the pace of lighting-industry change accelerated, said Mark Lien, L.C., CLEP, CLMC, HBDP, LEED BD&C, Director of Government & Industry Relations for OSRAM SYLVANIA. Today, however, change is often occurring faster than the existing process can accommodate, creating the potential for delayed application of new technologies. Dynamic spectral tuning is one of these new technologies, permitting programmed changes in the color temperature of the light being emitted, so that an outdoor LED installation can produce bright-white light during evening rush hour, then progressively warmer lighting as it gets later, to maintain visual comfort and effective visibility.

The third panelist – Janet Lennox Moyer, FIALD, a lighting designer and founder of the International Landscape Lighting Institute – pointed out that, even when the color temperature of an LED fixture is about the same as a legacy lamp’s, the LED’s light often appears to be less warm. She acknowledged that dynamic spectral tuning can reduce the disparity in appearance, but widespread application of that technology can occur only when standards exist.

The entire panel discussion is provided in two parts and is available for viewing free of charge on the National Lighting Bureau website. The Bureau is an independent, IRS-recognized not-for-profit, educational foundation that has served as a trusted lighting-information source since 1976. The Bureau’s services are made possible by the generous funding of its sponsors; professional societies, trade associations, manufacturers, and agencies of the U.S. government, including:

Obtain more information about the Bureau by visiting https://www.nlb.org or by contacting its staff at info@nlb.org or 301/587-9572.


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