as indicated [ below ]. A threshold marking helps identify the beginning of the runway that is available for landing . In some instances the landing threshold may be relocated or displaced . For narrower runways , the number of stripes can be as few as 4 for a 60 foot wide runway , or as many as 16 for a runway 200 feet or wider . A threshold marking shall be provided at the threshold of a paved instrument runway , and of a paved noninstrument runway where the code number is 3 or 4 and the runway is intended for use by international commercial air transport . The stripes of the threshold marking shall commence 6 m from the threshold . A runway threshold marking shall consist of a pattern of longitudinal stripes of uniform dimensions disposed symmetrically about the centre line of a runway as shown in [ the
figure ]. The touchdown zone markings identify the touchdown zone for landing operations and are coded to provide distance information in 500 feet ( 150m ) increments . These markings consist of groups of one , two , and three rectangular bars symmetrically arranged in pairs about the runway centerline , as shown in [ the figure ]. For runways having touchdown zone markings on both ends , those pairs of markings which extend
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