Roadways are one key area where the ‘LED revolution’ has left some faded soldiers still on the battlefieldBy Norma J. Frank
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In a recent issue of LD+A (May 2022), I described the results of an important study of LED exit sign useful life and its potential conflict with exit signs’ intended role to support navigation during an emergency. Completed in 2021, the study was conducted by the Light and Health Research Center (LHRC), funded by the McClung Lighting Research Foundation, and sponsored by my firm and the interNational Association of Lighting Management Companies (NALMCO).
Its results were suggestive of a potentially widespread problem in which exit signs are operational but failing to produce luminance considered sufficient for emergency conditions.
Using the word “problem” is likely understating things. Without hyperbole, I would call it a crisis. Nearly 25% of the roughly 350 field-tested exit signs showed luminances below the target threshold. Based on Department of Energy estimates, more than 40 million exit signs are installed in the U.S. If even just 10% produced insufficient luminances, this represents millions of signs that are operational but not doing their primary job related to safety.
What particularly makes it a crisis is that it’s not just about exit signs. Consider from a safety perspective how important maintaining proper light levels is in applications such as roadway and area lighting, stairwells, processing and manufacturing, hospitals, parking lots and garages, parks and public spaces, and tunnels. Then consider how important proper illumination is to productivity in offices and schools. Or how important proper color is for retail, healthcare, graphic design and printing.
The root of the problem is in the operating characteristics of the light source, specifically its failure modes. LED technology is wonderfully energy efficient, long lasting, resilient and controllable, with a form factor enabling diminutive and novel luminaire designs. Unfortunately, while it may be “install and forget” in that the light source is long-lasting and does not fail on the same mortality curve as traditional lamps with its averaging into a steady replacement rate, it does require maintenance. The issue with the failure mode is not always readily visible, showing up as lumen depreciation and color shift.
As a result, like the exit signs in the aforementioned study, an enormous quantity of LED luminaires are aging, but with uncertainty about when they should be replaced. Retaining installation of operating luminaires past their useful life may appear economical to the owner, but insufficient light levels are hazardous to design integrity and related occupant satisfaction, productivity and safety.
As a specific example, consider the nation’s more than 26 million streetlights. This market was an early and strong adopter of LED lighting, with a major driver being maintenance savings. In a 2015 survey by the Municipal Solid-State Street Lighting Consortium (MSSLC), respondents reported significant annual maintenance as well as energy cost savings.
While these are amazing benefits, again, a main mortality mode of the light source is problematic. Are these luminaires being replaced when they are no longer producing sufficient light levels required for traffic and pedestrian safety? A related issue is, typically, the luminaires were cleaned during lamp replacement, reducing luminaire dirt depreciation and helping to preserve light distribution; during cleaning, workers could also detect problems such as encroaching foliage. Are these luminaires being cleaned at all anymore?
All this is not a manufacturing problem. It is a maintenance problem. And it’s an industry problem in that by and large, owners are not being properly educated about their risks and responsibilities.
Several potential solutions come to mind:
Support and follow research. Additional research could help confirm this problem and its consequences. For example, a study similar to the exit sign study but targeted to a larger application such as streetlighting would be beneficial.
Favor maintenance-friendly products. More luminaires could be developed that maintain a constant light output based on owner requirements, with a readily visible catastrophic failure mode. The luminaire could perform this on a schedule or alternately could dynamically monitor output with an alarm indicating a need for replacement. Both of these technologies are readily available.
Maintenance is further facilitated with standardized components and connections, providing a systems manual to the owner, and enabling installed luminaires to be serviceable with readily available, easy-to-install components. This is not only beneficial for maintenance but also creates an upgrade aftermarket.
Engage in best practices. Besides favoring designs and luminaires that are easy to maintain, designers and specifiers should choose suppliers that have longevity and support their products. They should also advise owners about LED failure modes and recommend a proactive maintenance program to ensure the lighting system consistently satisfies the design intent not only upon installation but in the future.
Overall, the LED revolution was an astounding success, significantly reducing the nation’s electric costs and consumption while providing new capabilities and benefits. Now that the revolution has effectively won, it is time for the industry to consider potential impacts on occupant productivity and safety when the installed LED base ages past its useful life in part based on lumen depreciation. We cannot allow the LED revolution to succeed only for it to result in risks of poor lighting.