runway

A runway is a long, straight strip of hard surface, typically concrete or asphalt, constructed to support the weight and friction of landing and takeoff operations. Modern runways range from 1,000 metres to over 4,600 metres in length, depending on aircraft type, airport elevation, and climate. The surface must withstand repeated heavy axle loads, jet blast erosion, and the abrasive effect of rubber tires at high speed.

Runway construction involves multiple structural layers. Below the wearing course sits a binder course, base course, and subgrade, all engineered to distribute aircraft loads and manage water drainage. Thickness varies: commercial airport runways typically require 350 to 500 millimetres of asphalt or up to 250 millimetres of rigid concrete, depending on soil conditions and expected aircraft. The surface is crowned slightly to shed water toward perimeter drains.

Markings, Numbers, and Deterioration

Runway orientation is indicated by a two-digit number painted on the surface: runway 09 faces 090 degrees magnetic (east), runway 27 faces 270 degrees (west). When a runway can be used in both directions, each end is marked accordingly. White edge lines, centre lines, and touchdown zone markings serve precision approach and landing operations. Taxiway markings are yellow to distinguish them from runway white.

Deterioration occurs through fatigue cracking, rutting from repeated wheel paths, foreign object damage (FOD) from gravel or debris, and rubber deposit buildup. Jet blast leaves charred and oxidized surface material. Rain or standing water accelerates subsurface erosion. Maintenance includes regular sweeping, pressure washing, crack sealing, and planned overlays every 15 to 25 years depending on traffic volume and climate.

Runway inspection falls under the maintenance team. Visual surveys, high-speed friction testing with friction measurement equipment, and ground-penetrating radar surveys detect subsurface voids and moisture. Bearing strength is assessed using aircraft wheel load data and allowable pavement strength indexes. Closure for maintenance or weather is coordinated with air traffic control and flight operations; even short repairs create significant operational and financial impact.