Understanding taxiways, holding points and signs at airports

An Airbus rolls past the fence, stops just short of the runway and stays put, although no aircraft is landing anywhere in sight. In front of it: four yellow lines, a red sign with numbers, maybe a row of red lights in the asphalt. If you can read taxiways, holding points and signs at the airport, you understand such moments right away – and as a spotter you often know minutes ahead where an aircraft will show up next. This guide explains the logic behind taxiway names, the three sign colors, the markings on the ground and the lights that show the way at night and in fog.

Taxiways in one sentence

Taxiways are the connections between runways and aprons. Together with the runways they form the maneuvering area, meaning the area where aircraft move under their own power. The apron with parking positions and gates is not part of it – it has its own rules, often with its own apron control. On the maneuvering area, by contrast, every movement needs clearance from air traffic control, usually from ground control or the tower.

So that pilots, vehicle drivers and controllers can communicate without misunderstanding, every taxiway has a name that is used identically on signs, on the airport chart and on the radio. The basic rules come from ICAO Annex 14 to the Convention on International Civil Aviation, which covers aerodrome design and marking. That is why signs in Frankfurt, Zurich or Singapore look largely the same.

How taxiways get their names

The most important rule is simple: runways get numbers, taxiways get letters. The runway number is derived from its orientation – how that works is explained in the article Understanding runway designations. Plain numbers are therefore off limits for taxiways on the airfield, otherwise “Two Five” could mean a runway or a taxiway.

Small airports get by with a few letters: a parallel taxiway A, a few connections B, C, D. At large hubs the alphabet is not enough. There, letters are combined with numbers, for example N1, N2, N3 for the branches of a parallel taxiway N. So you can tell from the name alone which connections belong together. Typical ones are:

• Parallel taxiways along the runway, often with a single letter, or with a letter pair when there are two parallel taxiways.
• Connecting taxiways between the parallel taxiway and the runway, usually as a letter plus a number.
• Rapid exit taxiways that branch off the runway not at a right angle but at a slant – roughly an angle of 30 degrees. Landing aircraft can take them at higher speed and clear the runway faster for the next movement.
• Taxilanes on the apron that lead only to parking positions.

According to ICAO recommendations, some letters are avoided where possible because they are easily confused with other characters: the I with the one, the O with the zero, the X with the cross that marks closed areas. This is not entirely uniform worldwide, though – when in doubt, what counts is what is on the chart of the respective airport.

On the radio, every letter is spoken using the ICAO phonetic alphabet. N3 becomes “November Three”, L becomes “Lima”. If you have the alphabet in your ear, you can follow taxi clearances without effort.

The three sign colors

Signs on the airfield follow a color code that can be learned in a few minutes. One look at a sign tells you whether it is information or an obligation.

Color	Meaning	Typical content	What it means for you at the fence
Red with white lettering	Mandatory instruction sign	Runway designation like “07C-25C”, runway-holding position, “NO ENTRY”	The protected area begins here – no going further without clearance
Black with yellow lettering and border	Location sign	Name of the taxiway the aircraft is on, e.g. “N3”	Shows you exactly where an aircraft currently is
Yellow with black lettering and arrow	Direction or destination sign	Branching taxiways, routes to runways, apron or terminal	Tells you where the taxi route can lead at this point

In practice, signs before intersections often stand as a group: in the middle sits the black location sign, to its left the yellow direction signs for turns to the left, to its right those for turns to the right. The red mandatory sign, on the other hand, stands at the hold line itself, usually on both sides of the taxiway.

When a sign is not practical, for example on very wide surfaces, the information is also painted on the ground. These surface markings with lettering look like signs lying flat: white lettering on a red background for mandatory information, yellow lettering on a black background for locations. From the air and from elevated observation decks they are often easy to see.

Markings on the ground

Most lines on taxiways are yellow. That sets them apart from runways, whose markings are white. This alone tells you in photos and aerial images where the runway ends and the taxiway begins.

• Centerline: A solid yellow line guides the nose gear. In curves it follows the arc, and at branches it splits.
• Edge marking: Double yellow lines bound the taxiway where the pavement next to it is not meant for aircraft.
• Runway-holding position before the runway: Four yellow lines across the taxiway, two solid and two dashed. The solid ones are on the side where you wait; the dashed ones face the runway. Anyone leaving the runway crosses the marking from the dashed side; anyone heading for the runway needs clearance to do so.
• Ladder marking: On runways with a precision approach, there is a second holding point further back that looks like a ladder. It protects the sensitive area of the instrument landing system when all-weather procedures are in use in poor visibility. If this marking is longer than 60 meters, “CAT II” or “CAT III” is also painted on the ground.
• Intermediate holding position: A single dashed yellow line, usually at the intersection of two taxiways. This is where an aircraft waits when air traffic control sequences traffic between taxiways – it has nothing to do with the runway.

Why the second, set-back holding point exists is easier to understand once you know how an instrument approach works. That is explained in the article The ILS approach explained.

Lights on the taxiway

At night and in fog, lights take over the role of the lines. Here too a fixed color code applies, clearly distinct from runway lighting. An overall overview of all lights is given in the article Runway and taxiway lighting; here are the lights that matter for taxiways and holding points.

• Blue: Edge lights bound the taxiway at the sides. Many blue lights in the dark mean: taxiway, not runway.
• Green: Centerline lights are set into the pavement and guide the aircraft. In areas that belong to the runway or touch its ILS protection zone, they alternate between green and yellow.
• Red (stop bar): A row of red lights across the taxiway at the holding point. Air traffic control switches them on and off. Red means stop – that applies even if the clearance already came over the radio but the stop bar is still lit.
• Green behind the stop bar (lead-on lights): Coupled with the stop bar. When the red goes out, the green centerline lights beyond it come on and show the clear path toward the runway.
• Flashing yellow (runway guard lights): In pairs at the edge or as a row in the pavement. They warn of the nearby runway but grant neither permission nor prohibition. Because of their alternating flashing, they are often called “wig-wags”.

Stop bars are required above all in poor visibility, but at many airports they are also in operation at night or permanently. For you at the fence that is a handy signal: if the red lights go out and the green ones come on at a waiting aircraft, it is about to roll onto the runway.

What are you looking at?

Following taxi clearances on the radio

When you listen to aviation radio, the signs suddenly turn into a story. A typical taxi clearance names the destination (usually a runway-holding position before the runway) and the route over certain taxiways. In essence it sounds like this: the aircraft taxis via taxiways L and N to the holding point of a particular runway and waits there. On the radio, the runway-holding position is called “holding point”, by the way, and the instruction to wait before the runway is “hold short of runway”.

Important phrases you should know:

• “Taxi to holding point …” – Taxi to the named holding point.
• “Hold short of runway …” – Stop before the named runway, even if the route would continue.
• “Cross runway …” – The runway may be crossed.
• “Line up and wait” – Taxi onto the runway, line up and wait for takeoff clearance.
• “Vacate via …” – Leave the runway via a particular taxiway.

Which frequency you listen to for this depends on the airport; the basics are covered in Understanding aviation radio frequencies. The difference between delivery, ground and tower is explained in the article Delivery, ground, tower, approach, center. What legally applies when listening to aviation radio in Germany is explained in Listening to aviation radio: the legal situation.

From radio call to photo: step by step

An example: at Frankfurt Airport there are several parallel runways, and the middle one is designated 07C/25C. A taxiway that crosses this runway is therefore marked with a red “07C-25C” sign. At Munich Airport with its two parallel runways, you can see from the visitors’ hill how aircraft are guided between apron and runway. How aircraft get from the gate onto the taxiway in the first place is explained in the articles Pushback explained and Gates, passenger bridges and remote stands.

Why all the effort?

The many signs, lines and lights have a serious background. One of the most dangerous situations in airport operations is a runway incursion: an aircraft or vehicle ends up on a runway without permission while others are taking off or landing. Hold lines, red mandatory signs, stop bars and runway guard lights form several layers of protection so that exactly that does not happen. Vehicles on the airfield, such as the follow-me vehicle, are also subject to the same rules and need clearance before passing a holding point. In addition, safety areas at the runway end make sure that mistakes do not immediately become a disaster – more on that in the article Runway safety.

If you would like to see what all this looks like up close, you can join a guided tour at many airports. What to expect is described in Airport tour and apron bus ride.

What to keep in mind as a spotter

• Observe from the outside only. You can see holding points, signs and stop bars from the fence, from observation decks and spotter hills. The airfield itself is a security area. What is allowed is summarized in Is plane spotting allowed?.
• Signs are not a timetable. They show possible routes, not the actual route. Which route an aircraft takes is decided by the clearance.
• Fog changes the picture. With all-weather procedures, holding points set further back are used, stop bars are surely in operation and aircraft taxi more slowly.
• Charts can become outdated. Taxiways are rebuilt, renamed or closed. Rely on the current edition of the aerodrome chart and on notes in NOTAMs – how to read them is in Reading and understanding NOTAMs.
• Noting registrations is worth it. An aircraft standing at the holding point is the best opportunity to read the registration cleanly.

Conclusion

The airfield follows a clear grammar: runways carry numbers, taxiways letters. Red means mandatory, black says where you are, yellow shows where it leads. Four yellow lines protect the runway, a row of red lights stops everyone until the tower switches it off. If you know this grammar and also read the aerodrome chart and the radio, you see at the fence not just aircraft taxiing but understand where they are headed – and are more often in the right place at the right time.