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LRC issues guidance on LED area lighting intended to enhance safety (UPDATED)

April 17, 2020

The Lighting Energy Alliance at the Lighting Research Center was behind new research findings that suggest uniformity of lighting is more important than light levels for parking lot safety.

Maury Wright

Photo credit: Image courtesy of the Lighting Research Center at Rensselaer Polytechnic Institute. Modified with permission.

The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute has announced the availability of guidance for solid-state lighting (SSL) design in area lighting with the goal of enhancing safety and the perception of safety in parking lots. Researchers discovered that uniformity can be more important than light levels in safe LED-based lighting installation outdoors; that conclusion supports energy and cost savings as well through the possibility of reduced light levels in luminaires that operate for long hours each night.

One of the presumed benefits of LED-based outdoor lighting has always been improved uniformity due to the beam control achievable via optics that can go far beyond the reflective chambers used with legacy sources. We’ve written about numerous such area lighting installations including a Texas parking lot project back in 2016. Moreover, pilot installations, especially in the case of street lighting, have shown that the superior color rendering of LEDs relative to high-pressure sodium sources and broader, more uniform spectra could enable SSL projects to operate at lower light levels than those prescribed for legacy sources.

The new LRC document is entitled “Guide for Parking Lot Lighting: Maximizing Illuminance Uniformity to Promote Perceptions of Safety While Reducing Power Demand.” “Exterior lighting in parking lots should support the visibility of hazards — and reinforce perceptions of safety so that people are not afraid to use the space at night,” said Jennifer Brons, director of design demonstrations at the LRC and one of the authors of the new guide.

The Lighting Research Center (LRC) investigated various aspects of parking-lot lighting in a scaled physical model, testing uniformity, average illuminance, and CCT. (Photo credit: Image courtesy of the Lighting Research Center at Rensselaer Polytechnic Institute.)

The information in the guide includes curated research previously completed in the outdoor lighting area and also results of tests conducted on the RPI campus using a scale model of a typical parking lot. The researchers studied average illuminance ranging from 2.5–20 lx, and CCTs ranging from 2850–5800K. Among other learnings, the work revealed that a parking lot lit at an average of 2.5 lx with 2:1 uniformity offers a similar safety rating to one lit at an average of 20 lx but with a 15:1 uniformity ratio.

One of the important results of the parking lot work was the development of mathematical models that can predict brightness and safety. The LRC team has captured that data in the Parking Lot Lighting Safety Perception Calculator. Implemented in a Microsoft Excel file, the calculator can be used by specifiers working on outdoor area-lighting projects.

“By using perceived safety as a performance criterion, alternate lighting designs can be evaluated to minimize power demand while balancing other design criteria,” said John Bullough, director of transportation and safety lighting programs at the LRC. “Taking advantage of uniformity has implications not only for energy savings but also for minimizing light pollution.”

The LRC project was supported by the lab’s Lighting Energy Alliance including members Natural Resources Canada, Efficiency Vermont, Energize Connecticut, National Grid, Northwest Energy Efficiency Alliance, and ComEd. You can download the guide in PDF form directly from the LRC website. The calculator is also available for download. Loading that link in your browser will automatically download the file to your PC.

*Updated Apr. 23, 2020 for calculator link correction. LEDs Magazine regrets the error.

About the Author

Maury Wright | Editor in Chief

Maury Wright is an electronics engineer turned technology journalist, who has focused specifically on the LED & Lighting industry for the past decade. Wright first wrote for LEDs Magazine as a contractor in 2010, and took over as Editor-in-Chief in 2012. He has broad experience in technology areas ranging from microprocessors to digital media to wireless networks that he gained over 30 years in the trade press. Wright has experience running global editorial operations, such as during his tenure as worldwide editorial director of EDN Magazine, and has been instrumental in launching publication websites going back to the earliest days of the Internet. Wright has won numerous industry awards, including multiple ASBPE national awards for B2B journalism excellence, and has received finalist recognition for LEDs Magazine in the FOLIO Eddie Awards. He received a BS in electrical engineering from Auburn University.