A centerline is a visual marking (and often lighting) running along the center of an airport runway or taxiway, guiding pilots for safe alignment during all ground operations.
A centerline is a vital visual—and sometimes illuminated—marking that runs along the exact center of airport runways and taxiways. Its purpose is to provide precise lateral guidance for pilots, ensuring correct aircraft alignment during takeoff, landing, taxiing, and crossing. By keeping aircraft on the centerline, pilots maintain safe clearance from pavement edges and obstacles, reducing the risk of excursions or collisions.
Centerlines are present on all paved runways and taxiways at certified airports. On runways, they appear as white dashed stripes extending the entire length. On taxiways, the centerline is a solid yellow line. At major airports, centerline lights are embedded in the pavement to enhance visibility during low-visibility conditions such as fog or night.
Pilots rely on these markings for:
Both the International Civil Aviation Organization (ICAO) and the U.S. Federal Aviation Administration (FAA) provide strict standards for centerline markings. These standards dictate color, width, length, spacing, lighting, and placement, ensuring global uniformity and safety. Key references include ICAO Annex 14 and FAA Advisory Circulars.
Some airports use tactile centerlines—grooved or raised paint—for extra feedback, especially in low visibility. Pilots can feel these through the aircraft wheels, adding another layer of alignment assistance.
Analogy:
A centerline is like a highway lane marker. Drivers stay centered in their lane for safety; pilots follow the centerline to keep the aircraft safely on the paved surface.
Runway centerline markings are highly standardized. In the U.S., per FAA AIM 2-3-4 and AC 150/5340-1M, the marking is a series of white, non-retroreflective dashed stripes:
| Element | Measurement |
|---|---|
| Stripe Length | 120 ft (36.6 m) |
| Gap Between Stripes | 80 ft (24.4 m) |
| Stripe Width | 12–18 in (30–45 cm) |
| Stripe + Gap | 200 ft (60.96 m) |
ICAO standards are similar, with minor regional variations. Paint is durable and abrasion-resistant, sometimes with glass beads for night visibility.
Uniformity ensures pilots have consistent visual cues worldwide.
Pilots use runway centerlines to:
Example:
During a Category III instrument landing, pilots may only see the centerline lights and a few stripes—crucial for safe rollout.
Runway centerline lighting consists of in-pavement white lights:
Combined, markings and lights ensure visibility in all conditions.
Taxiway centerlines are solid yellow lines, 15–30 cm wide, running the length of the taxiway.
Regular maintenance ensures that markings remain clear.
Enhanced centerlines are used near runway holding positions, especially at busy airports:
Taxiway centerline lights are green in-pavement lights:
Example:
A pilot follows the yellow line from gate to runway, noting the enhanced centerline as the runway nears and stopping at the holding position.
| Feature | Runway Centerline | Taxiway Centerline |
|---|---|---|
| Color | White | Yellow |
| Marking Style | Dashed (120’ stripes, 80’ gaps) | Solid, continuous |
| Stripe Length | 120 ft (36.6 m) | N/A |
| Stripe Width | 12–18 in (30–45 cm) | 6–12 in (15–30 cm) |
| Lighting | White/red/white, red (last 3,000/1,000 ft) | Green (centerline lights, offset) |
| Enhanced Marking | N/A | Dashed lines near runway holdings |
| Operational Use | Takeoff, landing, rollout, RVR estimate | Taxi guidance, incursion prevention |
| Regulatory Reference | FAA AIM 2-3-4 | FAA AIM 2-3-7 |
Pilots estimate runway visual range (RVR) by counting visible centerline cycles (stripe + gap = 200 ft). For example, seeing four cycles means about 800 ft visibility.
Always check the airport’s Aeronautical Information Publication (AIP) for details.
| Term/Marking | Color | Line Style | Lighting | Key Use | Reference |
|---|---|---|---|---|---|
| Runway Centerline | White | Dashed (120’/80') | White (offset centerline lights) | Takeoff, landing, rollout | FAA AIM 2-3-4 |
| Taxiway Centerline | Yellow | Solid, continuous | Green (offset centerline lights) | Taxi guidance, ATC compliance | FAA AIM 2-3-7 |
Centerline lights are intentionally placed just to the side of the painted centerline. This offset allows for efficient maintenance—such as repainting the line without masking each light—and reduces the risk of repeated nosewheel impacts damaging both the lights and aircraft landing gear.
No. The centerline provides directional guidance, but it does not assure wingtip or tail clearance from obstacles, especially for larger or non-standard aircraft. Pilots must consider the entire aircraft footprint and may need wing walkers or marshallers in tight spaces.
An enhanced taxiway centerline features dashed lines flanking the standard yellow centerline as aircraft approach a runway holding position. This visual enhancement increases pilot awareness and helps prevent accidental runway incursions, especially in complex or low-visibility environments.
The basics are similar globally, but ICAO and FAA standards differ in details like stripe width, lighting, materials, and maintenance. Always consult the relevant Aeronautical Information Publication (AIP) for local specifications.
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