UK CAA sign standards (CAP 168)

The United Kingdom standard

In the United Kingdom, airfield signs are regulated by the UK Civil Aviation Authority (CAA) through CAP 168, Licensing of Aerodromes. This page draws on Edition 13. CAP 168 is the airport-licensing rulebook, and its Chapter 7, Aerodrome Signals is where the sign standards live.

Chapter 7 transposes ICAO Annex 14 Chapter 5.4 and Appendix 4 rather than writing an independent standard, so a CAP 168 sign is an Annex 14 sign — the same two colour-coded families, the same inscriptions. Edition 13 tracks Annex 14 up to and including its recent amendments, with a small number of deliberately UK-specific details noted below.

The two families in CAP 168

CAP 168 keeps the ICAO taxonomy exactly:

• Mandatory instruction signs — a white inscription on a red background. These cover the runway holding position, intermediate holding position and no-entry signs. The no-entry sign is the red disc with the white horizontal bar.
• Information signs — for location signs a yellow inscription on a black background; for direction, destination and runway-exit signs a black inscription on a yellow background. CAP 168 also covers the runway-vacated sign and the VOR aerodrome check-point sign in this family.

Where CAP 168 differs from ICAO

CAP 168 is a transposition, but the catalogued readings show a few places where it is stricter or more prescriptive than the current ICAO text:

• Sign-face height (an unresolved conflict in the source). Edition 13 is internally inconsistent on this point: Table 7.1D retains the older 2 × legend height minimum face height (400 / 600 / 800 mm), while Table 7.0(a) and Figure 7A.1 carry the ICAO Amendment 15 values of 1.5 × (300 / 450 / 600 mm). CAP 168 does not settle which governs. Wingframe takes the stricter 2 × reading as a conservative interpretation — a face that satisfies 2 × also satisfies 1.5 × — but this is our reading of a contradictory source, not an unequivocal UK requirement; confirm against the edition in force for a given aerodrome.
• Delineator width. The vertical delineator between adjoining same-colour signs is fixed at 3/4 of the character stroke width, a slightly heavier line than the ICAO proportion.
• Word spacing is pinned to exactly half the character height, rather than the ICAO 0.5–0.75 range.

Legend (character) heights themselves follow ICAO: 200, 300 and 400 mm keyed to the runway code, with matching 32, 48 and 64 mm stroke widths. Where a CAP 168 figure is undimensioned (for example the no-entry and runway-vacated symbols), the proportions are taken from the ICAO/EASA drawings — these are noted rather than given invented values.

How CAP 168 fits the wider picture

CAP 168 sits alongside EASA CS-ADR-DSN: both transpose Annex 14, and after Brexit the UK CAA maintains CAP 168 as the national standard rather than applying the EASA certification specifications directly. The regulations overview compares CAP 168 with ICAO, EASA, the FAA and the other national authorities.

Draw to the UK standard in Wingframe

Wingframe draws airfield guidance signs to the ICAO Annex 14 geometry that CAP 168 transposes — the reserved-red rule, the legend heights and stroke widths, and the family colours — so the sign you design matches the standard it will be built and inspected against. See what Wingframe does.