Use of LEDs has already caused at least one incident where a Delta aircraft landed on an LED edge lit parallel taxiway rather than the runway.
At the time of the incident the runway edge and center line lighting was operated at low intensity (step 1 of 5, equivalent a current of 2.8 amps). Both edge lights of the taxiway M were operated at high intensity (step 5 of 5, equivalent to a current of 6.6 amps) and the taxiway center line lights were operated a medium intensity (step 2 of 5, equivalent to a current of 3.4 amps). The taxiway lighting at the east end of taxiway M had been replaced with LED type lights in 2009 during an upgrade. Pilot comments had been received that the LED type lights appeared much brighter than the other original incandescent lights but no formal pilot input was collected. The FAA determined that pilots do not like intermixing incandescent and LED lights, but did not publish any standard for intermixing the lights.
Flight tests showed that it was challenging to identify the runway lights of runway 27R as the taxiway lights appeared much brighter. Aligned with runway 27L and side stepping with the same light settings as during the incident flight the runway center line lights were not identifyable and the taxiway lights were much more prominent. While on final to 27R the taxiway lights were still more prominent than the runway edge lights. At 500 feet AGL the runway center line lights were barely visible and it appeared several of them were out. The colour of the taxiway lights became distinguishable at about 500 feet AGL.
See
Incident: Delta Airlines B763 at Atlanta on Oct 19th 2009, landed on taxiway