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Research was conducted to determine the effective intensity of flashing lights that incorporate light-emitting diodes (LEDs). LEDs require less power and have the ability to flash without the addition of moving parts. Compared with incandescent bulbs, however, LEDs yield a different spectral output and a different intensity profile when flashing. To determine the effect of these differences on a viewer’s ability to detect the light, we examined LEDs to determine if they can successfully replace legacy technologies/assemblies on aircraft. The LED was displayed to naïve subjects to establish visibility thresholds using an automated system to drive the LED with variable intensity and duration. Experimental data were examined to determine which model for effective intensity (Allard, Modified Allard, or Blondel-Rey) is most appropriate for LEDs. Each of the methods was found to be applicable dependent upon the system being considered. Use of the Blondel-Rey method produced acceptable but conservative results.