Alternating Yellow and Green Taxiway Centerline as a Runway Safety Enhancement

This research effort was conducted to investigate and validate the suitability of installing alternating yellow and green taxiway centerline lights on taxiway segments located between the runway hold position marking and the runway centerline in the direction approaching the runway. This lighting configuration is the same configuration frequently used to identify the centerline of a taxiway exiting a runway, except that it is viewed from the opposite direction. This lighting configuration would serve as a visual cue to pilots and vehicle drivers that they are about to enter the runway environment/runway safety area (RSA). The objective of this research effort was to determine how the proposed lighting configuration would appear to pilots approaching the hold line (runway environment/RSA), if presently available lighting fixtures are adequate for the purpose, if present spacing standards are adequate for the purpose, if pilots interpret the purpose of the alternating yellow and green taxiway centerline lighting configuration correctly, and the cost factors involved in making such a change. The alternating yellow and green taxiway centerline lighting configuration was found to be suitable for various reasons. Presently available fixtures, such as the L-852 taxiway centerline fixture, were found to be adequate in color, intensity, and alignment, for this purpose, as long as they are installed, aligned, and maintained as required in the appropriate Advisory Circulars. Subjects were unanimous in judging the spacing as satisfactory for this purpose. The results of this research effort showed that subjects were able to recognize that there was some kind of transition at the point at which the lighting changed from green to the alternating pattern. The cost to modify a taxiway/runway entrance to the alternating yellow and green taxiway centerline configuration is dependent on the length of the taxiway section, the complexity of the intersection, and the number of fixtures available. Price estimates for replacing the appropriate filters, as well as other serviceable parts, ranged from $50 to $200 per fixture, including labor and parts. This price makes the alternating yellow and green taxiway centerline lighting configuration one of the cheapest alternatives for potentially reducing runway incursions compared to many of the more expensive stop bar or radar-based warning systems. Having considered all of the data and information gathered during this evaluation effort, illuminating the runway environment/RSA area with alternating yellow and green taxiway centerline fixtures was found to be a cost-efficient, easy to deploy tool that will assist in reducing runway incursions at those airports that have existing taxiway centerline lights.