19.3 Taxi Operations: Signs, Markings, Lighting, and Runway Incursion Avoidance

Taxiing is where the private pilot knowledge test tests runway incursion avoidance, and the questions are almost always decoded by two rules.

Rule one: runway markings are WHITE; taxiway markings are YELLOW. Centerlines, edge lines, hold lines, and direction markings painted in yellow belong to the taxiway world. Runway designators, centerlines, threshold bars, aiming points, and touchdown-zone bars are white.

Rule two: on a paired solid/dashed marking, the SOLID side is the restricted side. You hold on the solid side and you may cross from the dashed side without a clearance.

Airport signs — decode by color first

The pairing that trips candidates up is a black location sign sitting next to a yellow direction sign. Read the black one first — it tells you where you are — then the yellow one, which tells you where the turns go.

The markings that keep you out of trouble

• Runway holding position marking. Four yellow lines: two solid, two dashed. You approach from the dashed side and hold short on the solid side. At a towered airport you may not cross it onto the runway without a specific clearance, and hold-short instructions must be read back. This marking is also used on a taxiway to hold traffic clear of an intersecting runway.
• Holding position for an ILS critical area. Two solid yellow lines joined by pairs of perpendicular lines — it looks like a ladder. Hold here when instructed so your airframe does not distort the localizer or glideslope signal.
• Movement/non-movement area boundary marking. Two yellow lines, one solid and one dashed. The solid line is on the non-movement (ramp) side. Crossing from the ramp into the movement area needs a clearance at a towered airport.
• Taxiway centerline. A continuous yellow line. An enhanced centerline — the centerline flanked by dashed yellow lines — warns that you are approaching a runway holding position marking, typically within about 150 feet.
• Displaced threshold. White arrows leading to white arrowheads at a bar across the runway. The pavement before the displaced threshold is not available for landing, but it is usable for takeoff, and for rollout after landing from the other direction.
• Blast pad, overrun, or stopway. Yellow chevrons. Not usable for taxi, takeoff, or landing — chevrons mean stay off.

Wind indicators and airport lighting on the ground

Wind indicators (PA.II.D.K4) are the wind sock, the wind tee, and the tetrahedron, usually inside a segmented circle whose extended legs show the traffic pattern direction for each runway. The wind sock is the only one of the three that also shows wind strength; a tetrahedron may be manually positioned and should not be trusted blindly.

Aircraft lighting (PA.II.D.K5): the anticollision beacon goes on before engine start and stays on until shutdown — it is the signal that the propeller is a hazard. Position (navigation) lights are required from sunset to sunrise under 91.209. The taxi light is for taxiing; the landing light is normally added when entering or crossing a runway so you are conspicuous. Strobes are customarily off while taxiing near others and on when you take the runway.

Hot spots (PA.II.D.K6a) are labeled HS 1, HS 2 on FAA airport diagrams and described in the Chart Supplement. They mark intersections with a history of, or potential for, confusion and incursions. Studying the airport diagram before you start the engine is the single most effective incursion countermeasure, along with writing down the taxi clearance.

Entering or crossing runways (PA.II.D.K6c): at a towered airport you need a specific clearance for each runway you cross. A clearance to taxi to a destination does not authorize crossing any runway along the way. At a non-towered airport, self-announce on the CTAF and look before you enter — nobody else is separating you.

Night taxi (K6d) demands slower speeds, reliance on the blue taxiway edge lights and green taxiway centerline lights, and extra care because signs are harder to read. Low-visibility taxi (K6e) is where airports operate under a Surface Movement Guidance and Control System plan; ask for progressive taxi instructions rather than guessing.

Runway Status Lights (RWSL)

ACS element PA.III.A.K9 names Runway Status Lighting Systems. RWSL is a fully automated system driven by surveillance data. It has two states — red on, or off — and two subsystems a private pilot meets:

• Runway Entrance Lights (REL): in-pavement red lights along the taxiway centerline at the hold line and out to the runway edge. Illuminated red means the runway is unsafe to enter or cross — stop and remain stopped.
• Takeoff Hold Lights (THL): in-pavement red lights in the runway takeoff-hold area. Illuminated red means it is unsafe to begin the takeoff roll because traffic is on the runway ahead.

Three rules the AIM states plainly:

1. Never cross over illuminated red lights. If ATC has issued a clearance and the lights are red, stop, tell ATC you are holding for red lights, and re-confirm.
2. Do not proceed when the lights extinguish without an ATC clearance. RWSL verifies a clearance; it does not substitute for or convey one.
3. Expect to see the lights cycle on and off several times while you wait — that is normal as traffic moves.