Either after a landing or on the way to takeoff, pilots must maneuver the aircraft on the ground on a system of taxiways to and from the terminal and hangar areas. Taxiway lighting systems are provided for taxiing at night and also during the day when visibility is very poor, particularly at commercial service airports.
The following overall guidance should be applied in determining the lighting, marking, and signing visual aid requirements for taxiways: In order to avoid confusion with runways, taxiways must be clearly identified.
Runway exits need to be readily identified. This is particularly true for high-speed runway exits so that pilots can be able to locate these exits 1200 to 1500 ft before the turnoff point.
Adequate visual guidance along the taxiway must be provided.
Specific taxiways must be readily identified.
• The intersections between taxiways, the in runways and taxiways, and runway-taxiway crossings need to be clearly marked.
The complete taxiway route from the runway to the apron and from the apron to the runway should be easily identified. There are two primary types of lights used for the designation of taxiways. One type delineates the edges of taxiways and the other type delineates the centerline of the taxiway. In addition, there is an increasing use of lighting systems on taxiways, such as runway guard lights (RGLs) and stop bars, to identify intersections with runways, in an effort to reduce accidental incursions on to active runway environments.
Taxiway Edge Lights
Taxiway edge lights are elevated blue colored bidirectional lights usually located at intervals of not more than 200 ft on either side of the taxiway. The exact spacing is influenced by the physical layout of the taxiways. Straight sections of taxiways generally require edge light spacing in 200-ft intervals, or at least three lights equally spaced for taxiway straight line sections less than 200 ft in length.
Closer spacing is required on curves. Light fixtures are located not more than 10 ft from the edge of full strength pavement surfaces. Taxiway centerline lights are in-pavement bidirectional lights placed in equal intervals over taxiway centerline markings. Taxiway centerline lights are green, except in areas where the taxiway intersects with a runway, where the green and yellow lights are placed alternatively. Research and experience have demonstrated that guidance from centerline lights is superior to that from edge lights, particularly in low visibility conditions.
For normal exits, the centerline lights are terminated at the edge of the runway. At taxiway intersections the lights continue across the intersection. For long-radius high-speed exit taxiways, the taxiway lights are extended onto the runway from a point 200 ft back from the point of curvature (PC) of the taxiway to the point of tangency of the central curve of the taxiway. Within these limits the spacing of lights is 50 ft. These lights are offset 2 ft from the runway centerline lights and are gradually brought into alignment with the centerline of the taxiway.
Where the taxiways intersect with runways and aircraft are required to hold short of the runway, several yellow lights spaced at 5-ft intervals are placed transversely across the taxiway.
Runway Guard Lights
Runway guard lights (RGLs) are in-pavement lights located on taxiways at intersections of runways to alert pilots and operators of airfield ground vehicles that they are about to enter onto an active runway. RGLs are located across the width of the taxiway, approximately 2 ft from the entrance to a runway, spaced at approximately 10-ft intervals,
Runway Stop Bar
Similar to runway guard lights, runway stop bar lights are in-pavement lights on taxiways at intersections with runways. As opposed to RGLs that provide warning to pilots approaching a runway, runway stop bar lights are designed to act as ?stop? lights, on the taxiway not to enter the runway environment. Runway stop bar lights are activated with red illuminations during periods of runway occupancy or other instances where entrance from the taxiway to the runway is prohibited. In-pavement runway stop bar lighting is typically installed in conjunction with elevated runway guard lights located outside the width of the pavement.