Airport operations — markings, signs, lighting, runway incursion
**Runway markings** are white: runway designator (numbered per magnetic bearing /10), centerline, threshold, aiming point, and touchdown zone. **Taxiway markings** are yellow: centerline, edge, and holding-position markings (four yellow lines: two solid, two dashed — dashed side may be crossed).
**Airport signs:** Mandatory instruction signs are red with white inscription (e.g., '15-33' at a runway holding position). Location signs are black with yellow inscription. Direction signs are yellow with black inscription.
**Light signals (AIM 4-3-13)** when radio-out: steady green — cleared to land/takeoff; flashing green — cleared to taxi/return for landing; steady red — stop/give way; flashing red — taxi clear of runway/airport unsafe; flashing white — return to starting point on airport; alternating red-green — exercise extreme caution.
**Runway incursion prevention (AC 91-73B):** always read back hold-short instructions, confirm aircraft location on a taxi diagram, never cross a runway holding-position marking without an explicit clearance, and make position reports at non-towered fields on CTAF 10 miles out, entering downwind, base, final, and clear of the runway.