What are taxiway designation signs?
Every taxiway has a name, and the signs repeat it. A short designator of letters or a letter and number, shown in yellow on black to say where you are, and in black on yellow to say where a taxiway leads.
A taxiway designation sign is simply a sign that carries a taxiway's name. The name, called the designator, is what a pilot reads against the airport chart and the controller's clearance, so it has to be short, unique and impossible to misread. The signs themselves are the ones covered in earlier entries; this entry is about what goes on them and why.
1How a taxiway is named
A designator is a letter, letters, or a letter or letters followed by a number. A main taxiway is typically a letter, such as A, and its connectors add a number, such as A1 and A2. Numbers on their own are reserved for runways, so a pilot never has to wonder whether a bare number is a runway or a taxiway.
2Letters to avoid
The letters I and O are avoided because they are easily read as the numerals 1 and 0, especially on a small sign at night. X is commonly kept to mark a closed taxiway, so it is avoided as a name too.
3Where the designator appears
On a location sign it is yellow on a black panel with no arrow (and a yellow border where it stands alone), answering which taxiway this is. On direction and destination signs it is black on yellow, with an arrow, answering which way to a taxiway. Putting the same designator on both lets a pilot match what they are on with where they are going.
| Element | Rule |
|---|---|
| Designator | A letter, letters, or letter(s) followed by a number, e.g. A, B, A1 |
| Numbers alone | Kept for runway designation |
| Letters to avoid | I and O (read as 1 and 0); X conventionally means closed |
| Sign that shows it | Location sign: yellow inscription on black, no arrow; yellow border where stand-alone |
| Also shown on | Direction and destination signs: black inscription on yellow, with an arrow |
| Placed | At the taxiway intersection, confirming the taxiway the aircraft is on |
Frequently Asked Questions
Q1What is a taxiway designator?
The name of a taxiway: a letter, letters, or a letter or letters followed by a number, such as A, B or A1. Numbers alone are kept for runways.
Q2Which sign shows the taxiway you are on?
The location sign: a black panel with yellow inscription (and a yellow border where it stands alone), carrying the taxiway designator and no arrow.
Q3Why are the letters I and O avoided in taxiway names?
They are easily misread as the numerals 1 and 0. X is also conventionally kept to mark a closed taxiway, so it is avoided too.
Q4Where else does the designator appear on signs?
Direction and destination signs show it in black on yellow, next to an arrow, to tell pilots which taxiway lies in each direction.
See It. Understand It. Then Learn How to Engineer It.
Recognising an AGL system visually is the first step. The next step is knowing how to design, install, test, commission and maintain them correctly.
Build Practical AGL Engineering Skills
Go deeper with structured training from Precision AGL Academy, covering:
Learn how each light, sign and circuit works as part of a complete airport lighting system, not just as an isolated diagram.