Sections of a runway
There are runway markings.
- The runway thresholds are markings across the runway that denote the beginning and end of the designated space for landing and takeoff under non-emergency conditions.
- The runway safety area is the cleared, smoothed and the graded area around the paved runway. It is kept free from any obstacles that might impede flight or ground roll of aircraft.
- The runway is the surface from threshold to threshold, which typically features threshold markings, numbers, and centerlines, but not overrun areas at both ends.
- Blast pads, also known as overrun areas or stop ways, are often constructed just before the start of a runway where jet blast produced by large planes during the takeoff roll could otherwise erode the ground and eventually damage the runway. Overrun areas are also constructed at the end of runways as emergency space to slowly stop planes that overrun the runway on a landing gone wrong, or to slowly stop a plane on a rejected takeoff or a takeoff gone wrong. Blast pads are often not as strong as the main paved surface of the runway and are marked with yellow chevrons. Planes are not allowed to taxi, take off or land on blast pads, except in an emergency.
- Displaced thresholds may be used for taxiing, takeoff, and landing rollout, but not for a touchdown. A displaced threshold often exists because obstacles just before the runway, runway strength, or noise restrictions may make the beginning section of runway unsuitable for landings. It is marked with white paint arrows that lead up to the beginning of the landing portion of the runway
There are runway markings and signs on most large runways. Larger runways have a distance remaining sign (black box with white numbers). This sign uses a single number to indicate the thousands of feet remaining so 7 will indicate 7,000 ft (2,134 m) remaining. The runway threshold is marked by a line of green lights.
There are three types of runways:
- Visual runways are used at small airstrips and are usually just a strip of grass, gravel, ice, asphalt, or concrete. Although there are usually no markings on a visual runway, they may have threshold markings, designators, and centerlines. Additionally, they do not provide an instrument-based landing procedure; pilots must be able to see the runway to use it. Also, radio communication may not be available and pilots must be self-reliant.
- Non-precision instrument runways are often used at small- to medium-sized airports. These runways, depending on the surface, may be marked with threshold markings, designators, centerlines, and sometimes a 1,000 ft (305 m) mark (known as an aiming point, sometimes installed at 1,500 ft (457 m)). They provide horizontal position guidance to planes on instrument approach via Non-directional beacon, VHF omnidirectional range, Global Positioning System, etc.
- Precision instrument runways, which are found in medium- and large-size airports, consist of a blast pad/stopway (optional, for airports handling jets), threshold, designator, centerline, aiming point, and 500 ft (152 m), 1,000 ft (305 m)/1,500 ft (457 m), 2,000 ft (610 m), 2,500 ft (762 m), and 3,000 ft (914 m) touchdown zone marks. Precision runways provide both horizontal and vertical guidance for instrument approaches.