AIM
4/20/23
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7
Airport Marking Aids and Signs
FIG 2
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5
Runway Shoulder Markings
RUNWAY THRESHOLD
MIDPOINT OF
RUNWAY
SHOULDER
SHOULDER
RUNWAY
45°
45°
45°
45°
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4. Taxiway Markings
a. General.
All taxiways should have centerline markings and runway holding position markings whenever
they intersect a runway. Taxiway edge markings are present whenever there is a need to separate the taxiway from
a pavement that is not intended for aircraft use or to delineate the edge of the taxiway. Taxiways may also have
shoulder markings and holding position markings for Instrument Landing System (ILS) critical areas and
taxiway/taxiway intersection markings.
REFERENCE
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AIM, Para 2
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5, Holding Position Markings.
b. Taxiway Centerline.
1. Normal Centerline.
The taxiway centerline is a single continuous yellow line, 6 inches (15 cm) to 12
inches (30 cm) in width. This provides a visual cue to permit taxiing along a designated path. Ideally, the aircraft
should be kept centered over this line during taxi. However, being centered on the taxiway centerline does not
guarantee wingtip clearance with other aircraft or other objects.
2. Enhanced Centerline.
At some airports, mostly the larger commercial service airports, an enhanced
taxiway centerline will be used. The enhanced taxiway centerline marking consists of a parallel line of yellow
dashes on either side of the normal taxiway centerline. The taxiway centerlines are enhanced for a maximum of
150 feet prior to a runway holding position marking. The purpose of this enhancement is to warn the pilot that
he/she is approaching a runway holding position marking and should prepare to stop unless he/she has been
cleared onto or across the runway by ATC. (See FIG 2
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8.)
c. Taxiway Edge Markings.
Taxiway edge markings are used to define the edge of the taxiway. They are
primarily used when the taxiway edge does not correspond with the edge of the pavement. There are two types
of markings depending upon whether the aircraft is supposed to cross the taxiway edge: