Lighting is a vast and complex topic, yet despite the confusion that surrounds LED technology, it’s clear we’re failing in a big way in its safe application and deployment. Nowhere is this more evident than with street lighting.
Although LED technology has enabled the profuse use of cheap light with energy, operational and maintenance savings appealing to municipalities around the world, such light happens to be brighter, more light-polluting and disruptive than the light it commonly replaces, causing many issues.
How can LED lighting, as applied today, be considered an improvement if it injures eye tissue, prevents quality sleep, causes pain and discomfort, harms health, impairs vision, hinders wayfinding, jeopardizes driving, compromises safety and security, degrades the ambience and atmosphere of neighborhoods, historic sites and architecture, puts flora and fauna at risk, threatens eco/astro tourism, worsens light pollution and steals away the stars in the sky?
Quite simply, it doesn’t matter how energy efficient a light source is, how long it’s lifespan, or how economic it is to operate and maintain – if it causes degradation and harm it’s a false economy.
While the adverse effects of blue wavelengths of light at night can no longer be dismissed, cool white LEDs are also infamous for their harsh, clinical, phototoxic light, strong contrast, blinding brightness and dangerous disability glare. Cheap and poorly designed LED luminaires can produce non-uniform light distribution, unwanted light trespass, flicker, and electromagnetic interference. Also, due to the intensity of light emitted, the chips in an LED array need to be hidden from the naked eye. Furthermore, although there’s less upwards light spill, shorter blue wavelengths of light directed at the ground readily bounce back into the atmosphere increasing light pollution.
It’s specious to claim bright white lighting improves safety and security, and we need to be careful about declaring “improved” light quality too. Such statements need to be questioned and the full equation understood. Education and transparency are key so people understand what this involves. Emerging evidence and millions of years of evolution counter these assertions. Indeed, the more we discover about photobiology, chronobiology, and human vision, the more obvious it is that lighting our streets brightly at night to look like day is misguided.
Biology on Earth developed with light/dark cycles, and like many other organisms, humans are exquisitely sensitive to light. Our health hinges on using the least disruptive light at the night, and restorative rest depends on complete darkness. This means artificial light needs to be as biologically responsible as possible.
Complicating matters further, there’s still much we need to learn about light in general and how the body responds to it. A paradigm shift in our use of light is necessary because light has the same powerful impact on the human body as pharmaceuticals. By default, the lighting industry has a responsibility to robustly test LED products to prove their safety and suitability before they enter the market.
So, what does responsible street lighting look like? Ideally, it’s shielded, indirect, soft on the eyes, evenly distributed, and as dim as practical – just the right amount of light where and when needed. LED lights should be no brighter than the light it replaces, with a similar or improved scotopic/phototopic (S/P) ratio of 0.4 to 0.6 (S/P ratio characterizes how much light emitted from a light source is useful to the human eye under scotopic vision and how much light pollution can be expected). The light is warm (2200 K or lower) with an appropriate spectral power distribution (minimal blue and green wavelengths) and it provides adequate color rendering. Thankfully, there are innovative and visionary companies leading the way.
