Shirley Coyle, President of Cree Canada, recently contributed her thoughts to Lighting Design & Application in response to a request to chime in on the American Medical Association’s recent guidelines for LED outdoor lighting.
She points out that basing recommendations on correlated color temperature (CCT) is flawed:
On the issue of safety, the most obvious flaw of the concerns raised is that CCT is not the issue at all — CCT is an overly simplistic value that describes the colour appearance of a light source, and for these issues the important metric to consider is the specific blue content, and more specifically the melanopic response, which cannot be captured in CCT. And along with spectral content, consideration has to be given to dosage, duration, and time of day.
She points out that the leading health issue is driver and pedestrian safety:
So there is a disconnect here between real lighting science and those leading the outcry on the basis of CCT. Fifty percent of fatal collisions happen at night time even though only 25% of roadway travel happens at night time. There is a statistics-based consensus that roadway lighting decreases night time collision rates. We light roadways primarily for safety reasons: the goal is to use well-designed roadway lighting to improve visibility for drivers, including their ability to detect other vehicles, pedestrians and cyclists.
Check it out here.