Definition

Threshold. The beginning of that portion of the runway usable for landing.

Source: ICAO Annex 14: Aerodromes

Decription

The threshold is normally located at the extremity of a runway, if there are no obstacles penetrating above the approach surface. In some cases, however, due to local conditions it may be desirable to displace the threshold temporarily or permanently. Factors to be considered include:

• obstacles near the approach path (including mobile objects such as vehicles or trains).
• the reference datum of the ILS/MLS.
• pavement characteristics.

The threshold is often used for a reference when establishing the location of various lighting and marking elements, such as: