A hold-short line is a painted marking on a taxiway that tells pilots exactly where to stop before entering an active runway. Crossing it without an explicit clearance from air traffic control (ATC) is a runway incursion, one of the most serious safety violations in aviation.
How It Works#
The hold-short line consists of four yellow lines painted across the taxiway: two solid lines on the runway side and two dashed lines on the taxiway side. This pattern has a specific logic. The solid lines face the direction you must not cross without clearance. The dashed lines face the direction you are free to proceed from.
The marking is officially called a runway holding position marking in FAA Advisory Circular 150/5340-1. It appears at every taxiway-runway intersection at controlled and uncontrolled airports. At complex airports, you may also find hold-short lines protecting instrument landing system (ILS) critical areas and intersecting taxiways.
Pilots must stop with the entire aircraft behind the hold-short line. This includes the tail. An aircraft that stops with its nose at the line but its tail hanging into the runway environment has still violated the boundary. Wingspan and aircraft length both factor into where a crew decides to stop.
At night or in low visibility, hold-short lines are supplemented by runway guard lights: a pair of alternating flashing yellow lights embedded in or flanking the taxiway at the holding position. These make the boundary unmistakable even when painted markings are hard to see.
Example in Aviation#
A Cessna 172 is taxiing to runway 28 at a towered airport. Ground control clears the pilot to taxi to runway 28 and hold short. The pilot stops with the nose wheel behind the hold-short line and contacts the tower. Tower is sequencing arriving traffic and has not yet issued a takeoff clearance. The pilot waits. Only after tower says "Cessna 123AB, runway 28, cleared for takeoff" may the pilot cross the line and enter the runway.
If the pilot had rolled across the hold-short line while tower was still working that arriving traffic, it would constitute a runway incursion, putting both aircraft at serious risk.
Why It Matters#
Runway incursions are a leading cause of fatal accidents at airports worldwide. The hold-short line is the last physical boundary between an aircraft on the ground and the high-speed environment of an active runway. Respecting it is not a formality. It is a hard safety barrier.
Student pilots learn early that a clearance to taxi does not include a clearance to cross a runway. Each hold-short line requires its own explicit clearance from ATC. Understanding this distinction prevents the most common type of incursion.
Key Takeaways#
- Two solid lines face the runway; two dashed lines face the taxiway.
- Never cross a hold-short line without an explicit ATC clearance.
- Stop the entire aircraft behind the line, including the tail.
- Runway guard lights supplement painted markings in low visibility.
- A taxi clearance does not include clearance to cross a runway hold-short line.