The AMA's recent guidance on proper installation and CCT of outdoor SSL would be better left for the lighting industry experts to determine, opines MAURY WRIGHT.
You may have read that at its recent annual meeting, the US-based American Medical Association (AMA) issued a document with guidance or recommendations for municipalities installing outdoor solid-state lighting (SSL). The guidance suggests that municipalities only install LED-based lighting at a warm CCT of 3000K or lower. The document also makes recommendations about beam angle. But there is no evidence that the AMA has carefully studied the pertinent outdoor-lighting issues, and frankly the organization is overstepping its bounds in weighing in on the topic.
The fact is that the Illuminating Engineering Society (IES) has a constantly-ongoing and comprehensive effort focused on the issue of street and area lighting. The IES diligently explores topics from the physiology of the human eye and visual system to dark-sky-friendly lighting and more.
The AMA, and other opponents of cooler-CCT light with relatively more blue energy, invariably only look at one side of the situation. These organizations consistently miss the point that the reason we have artificial light outdoors at night is the safety of people - both actual safety in terms of fewer injurious accidents and perceived or preventative safety enabled through better visibility that discourages crime and allows citizens to more clearly see and react to potentially dangerous situations.
Now I'm not suggesting that safety for pedestrians or drivers at night trumps the need for lighting that is also safe to our eyes and wellbeing. We certainly need to install lighting that is safe for typical exposure, even, say, for a police officer who patrols under artificial lighting for long hours at night. But even such exposure doesn't typically involve people looking directly at installed lights, and much of the clamor for warmer CCTs refers to research that isn't indicative of a typical use case.
I still believe IES research will ultimately document that we can operate cooler-CCT lights at lower levels than warmer-CCT lights while delivering improved visibility. That scenario would mean lower energy use, and perhaps a relatively similar amount of energy in the blue spectrum. I have been to test sites that convinced me that I see far better under 4000K light than I do under 3000K light.
There are, of course, cost issues as well. In the past, cooler lights have been cheaper and more efficient. The warm-CCT proponents are correct that those gaps are narrowing.
But the cost issues go deeper and the AMA didn't appear to even consider the impact of its recommendations on the viability of outdoor area lighting installations. The organization has also recommended what equates to a very narrow beam pattern to guard against disability glare. That recommendation, however, could completely change the equation on outdoor lighting pole spacing and total system cost. Indeed, poles and installation cost municipalities far more than do luminaires.
Now my feelings about cooler- or warmer-CCT may ultimately be all wrong. But I believe I'm dead right in suggesting that the AMA, despite good intentions, should leave LED recommended practices on outdoor lighting to the IES. The AMA will simply further confuse municipalities struggling to find their way with SSL projects.
Maury Wright, Editor