There are 4 main types of runway signs you should be familiar with before venturing out onto the airport: Runway Distance Remaining Signs, Runway Location Signs, Runway Safety Area Boundary Signs, and Runway Holding Position Signs.
Runway Holding Position Signs
These signs, with white lettering on a red background, are Mandatory in Nature, and are found at the intersections of runways and taxiways, and in the case of intersecting runways, at intersections of two runways. "Mandatory in nature" means that these signs act as the equivalent of stop signs; when you see one, hold your position. If you pass this sign, and the associated runway holding line marked on the ground, you will be entering an active runway, which can be a very dangerous place if you're not supposed to be there!
Whenever you approach a runway holding position sign be prepared to come to a complete stop and wait to hear your call sign and the phrase "cleared to cross runway [insert runway designator here]." Make sure you hear your call sign and don't just assume a crossing instruction is for you.
You may receive a runway crossing clearance as part of your initial taxi instructions, for instance, "Warrior 41459, taxi to runway 26 via Bravo, cross Runway 31 at Bravo." In this case, you would be cleared to cross runway 31 as you came to it. If your taxi instruction is "Warrior 41459, taxi to runway 26 via Bravo, hold short of runway 31," or just "Warrior 41459, taxi to runway 26 via Bravo," you are Not cleared to cross runway 31, and should not pass the runway holding position sign and associated holding line marked on the ground.
At an uncontrolled field, come to a complete stop, state your position and intention clearly over the common traffic advisory frequency, and check all directions to ensure no traffic is in opposition to your movements before you enter an active runway.
You are on Taxiway Alpha, about to enter an active runway. To the left of you is the threshold of runway 18, to the right is the threshold of runway 36.
The numbers on the runway holding position sign correspond to the runway designators, and are arranged to show the location of each runways' threshold. For example, a sign reading "18-36" indicates that the threshold for runway 18 is to the left, and the threshold for runway 36 is to the right. Often these signs are also paired with a taxiway sign to remind the pilot which taxiway they are currently on.
In the case that you are located at a taxiway intersection at the beginning of the runway, the sign will only have one runway designator on it, the runway on which you would be pulling out onto if you passed the sign.
You are at the approach end of Runway 14, and are currently on taxiway Alpha.
In the case that there are intersecting runways, runway holding position signs will have the standard runway designators, as well as arrows showing the approximate alignment of each runway indicated. The arrow also points towards the threshold of the runway designator indicated next to it.
See image to the right for representation of what the arrows indicate.
Runway Approach Area Holding Position Sign
At some airports, it may be necessary for a pilot to hold short of a runway in an area displaced from the normal position at the runway threshold. In this case, there will be an approach or departure area in which you will be asked to hold short to prevent you from entering a runway safety area and endangering yourself or anyone operating on the active runway. Rather than holding at the usual runway holding position sign, you will see a red sign with white lettering dictating the runway designator for the aircraft and the letters "APCH".
Runway Approach Area Holding Position Sign
Remember, red signs are mandatory in nature and the runway approach area holding sign should be treated exactly the same as a normal runway holding position sign. Do not pass this sign and area without being cleared to do so!
Runway Safety Area Boundary Signs
The runway Safety Area (RSA) is the paved area directly abutting the runway that is deemed suitable for an aircraft to traverse safely (or with minimal damage) in case of an emergency causing unexpected deviation from the proper runway environment.
At some airports, upon exiting the runway at a taxiway intersection you will see, in addition to the standard taxiway designator sign, a runway safety area boundary sign.
This sign is a yellow background with black markings representing the runway holding line (picture below). It will that face the runway and be visible to you only when exiting the runway.
These signs are generally present at airports were the tower may ask you to report your position once clear of the runway, or in areas where the tower can not see an aircrafts' position. Keep in mind that if this sign is not present, runway holding position markings on the ground also identify the boundary of the runway safety area for aircraft exiting the runway.
RSA boundary sign
Runway Location Signs
These signs, positioned along the side of the runway, act as a supplement to the pilot's magnetic compass and heading indicator in clarifying which runway the pilot is on. These signs are typically only used in areas where the proximity of several runways could cause confusion as to which runway a pilot is on.
Runway locations signs are black, with yellow numbering and a yellow border.
Runway Location Sign
Runway Distance Remaining Signs
These signs are positioned along the side(s) of a runway and indicate to the pilot the length of the landing runway remaining. The signs are advisory in nature and have a black background with white lettering. The number displayed indicates the feet remaining rounded to the nearest thousand. An important note, the last sign, bearing a white numeral "1" may be located as close as 950' from the end of the runway.
Runway Distance Remaining
