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Maximum Luminous Intensity of LED-lighted X signs for Airport Runways



Yoshi Ohno, Maritoni Litorja, C Cameron Miller


This is a report for Inter-agency agreement 693KA9-18-N-00023 "Maximum Luminous Intensity for LED Signaling in an Airport Environment" by Federal Aviation Administration (FAA) and National Institute of Standards and Technology (NIST). The LED-based lighted X signs recently introduced at many airports are perceived too bright by pilots, causing glare and making it difficult to recognize the X character. The objective of the study is to determine the acceptable level of maximum luminous intensity of LED-lighted X signs that maintains clear visibility of the lighted X sign. A theoretical study with literature review was first made (Part 1). Then vision experiments were conducted using pilots as subjects (Part 2). The methods and results of these studies are reported.
NIST Interagency/Internal Report (NISTIR) - 8321
Report Number


airport, signaling, lighted X sign, luminous intensity, glare, visibility


Ohno, Y. , Litorja, M. and Miller, C. (2024), Maximum Luminous Intensity of LED-lighted X signs for Airport Runways, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed July 12, 2024)


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Created June 12, 2024