Identification Techniques to Reduce Confusion Between Taxiways and Adjacent Runways

The National Transportation Safety Board accident/incident database and the Aviation Safety Reporting System have reported pilots mistakenly landing on the taxiways adjacent to runways. As of August 23, 2007, 267 such events have occurred at 110 airports in the United States. These inadvertent landings create a safety hazard that must be eliminated. This technical note provides guidance on techniques that can be implemented at airports to reduce or eliminate this problem. Two scenarios were considered during this research effort: (1) prevent the pilot from inadvertently lining up with the taxiway during the approach, and (2) prevent the pilot from landing on the taxiway if the first effort fails. Four visual aid enhancements were tested at Seattle-Tacoma International Airport and Palm Beach International Airport: an elevated lighted X, artificial turf, omnidirectional runway end identifier lights, and an in-pavement lighted X. Each piece of equipment was placed on the taxiway and was evaluated one at a time while making final approaches to the runway with the exception of the artificial turf and omnidirectional lights, which were turned on constantly. Based on the results, it was concluded that an elevated lighted X and an in-pavement lighted X were seen at an average distance of 4.5 nm. Omnidirectional lights and green artificial turf were seen at a distance of 5.0 nm.

To eliminate similar occurrences at Lincoln Airport, the Airport Authority has implemented installation of nonstandard taxiway markings, such as surface-painted A, surface-painted TAXI ONLY, and a painted serpentine marking. This investigation found that all solutions have some deficiencies: the painted A looks similar to a displaced threshold chevron, the word TAXI in the painted TAXI ONLY is sufficient to perform the intended task, and the serpentine markings were not clearly visible from the air. It was concluded that airport geometry is a major causal factor in all these incidents and should be eliminated in the early design phases of the airport. 

DOT/FAA/AR-TN07/54
Authors: James W. Patterson, Jr. & Renee N. Frierson