What is a Threshold Marking?

A threshold marking is a set of white longitudinal stripes that shows where the usable part of a paved runway begins.

ICAO defines the threshold as the beginning of that portion of the runway usable for landing. The runway threshold page covers the threshold itself, its position and its lights. This page covers the paint.

What the standards require

ICAO writes the application and location as Standards (“shall”). EASA writes the same items as “should”. The FAA sets its requirement by approach category in Table 2-1.

How many stripes

The runway width sets the number of stripes. The stripes sit symmetrically about the centre line.

ICAO and EASA allow a different pattern on some runways. These are non-precision and non-instrument runways at least 45 m wide (Annex 14 Figure 5-2 (C), CS-ADR-DSN Figure L-1 (C)).

For a non-standard width, the FAA continues the stripe and gap pattern from the centre line. The outermost stripe must be no closer than 4 ft (1.2 m) to the runway edge. A 125 ft (38 m) runway gets 10 stripes. The pattern never reaches more than 92 ft (27 m) from the centre line.

How the stripes are laid out

• Lateral extent. ICAO and EASA say the stripes extend to within 3 m of the runway edge. They stop at 27 m from the centre line if that is closer.
• Centre gap. The FAA doubles the gap between the two stripes nearest the centre line. Their outer edges are 11.5 ft (3.5 m) apart. ICAO and EASA also use a double spacing there. This leaves room for the runway edge marking beside the outer stripes in the FAA pattern.
• Designation. If the runway designation is inside the threshold marking, at least three stripes remain on each side of the centre line. The gap there is 22.5 m. Where the designation is above the threshold marking, the stripes continue across the runway.

Threshold marking, threshold bar and displaced threshold

ICAO and EASA recommend a transverse stripe, at least 1.80 m wide, in two cases. The threshold is displaced from the runway end, or the runway end is not square with the centre line. A permanent displacement also gets arrows on the runway before the threshold (Annex 14, 5.2.4.6 to 5.2.4.8).

The FAA uses a white threshold bar, 10 ft (3.1 m) wide, between the runway edges. The AC requires it when a displaced threshold, blast pad, stopway, EMAS or aligned taxiway lies on the approach side of the threshold (2.9.1). The bar also applies where more than 5 ft (1.5 m) of pavement lies before the threshold. A pilot could take it for runway, or it could be weaker than the runway (2.5, item 4). The stripes still begin 6 m (20 ft) past the threshold. Older FAA practice moved them to 30 ft (9 m) when a bar was painted.

See displaced threshold for the arrows, the declared distances and the lights. A paved area before the threshold can also carry yellow chevrons. The blast pad page covers them.

Telling it apart from its neighbours

• Threshold marking. Longitudinal stripes, at the threshold, white.
• Runway designation. A two-digit number, at the threshold. The runway designation page covers it.
• Aiming point marking. Two bars, much further down the runway. CS ADR-DSN.L.540 places them 150 m to 400 m from the threshold, by landing distance available.
• Threshold lights. Green lights across the runway. They are lights and not paint. The threshold light page covers them.

The runway marking page shows the full runway scheme.

Temporary threshold markings

A runway returns to use before its final paint is on. The EASA guidance says threshold markings are painted as soon as possible, using temporary materials before they are made permanent (GM1 ADR.OPS.B.070(c)(5)). A temporary threshold during an overlay is identified by a 3.6 m wide transverse stripe (AMC1 ADR.OPS.B.070(c)(5)).

When a threshold moves, the FAA removes the old markings instead of painting them over. It removes the old threshold marking in one larger rectangular area, so that no trace misleads a pilot.

Surveying and checking a threshold marking

EASA survey guidance covers marked thresholds, for example displaced thresholds. It says to take these markings as the threshold points (GM2 ADR.OPS.A.005(a)).

A check of the marking looks at these items:

• The count of stripes matches the runway width.
• The stripes begin 6 m (20 ft) past the threshold and are symmetrical about the centre line.
• The stripes are white, even in length, and not worn through.
• Any transverse stripe or threshold bar is present where the threshold is displaced.
• Old markings are fully removed after a threshold move.

TarmacView’s runway surface scan captures georeferenced imagery of the pavement. A person reads the markings on that imagery. The service is in development and is not offered yet.