ICAO DOC 9157 Aerodrome Design Manual Part 6 Frangibility Ed 1
At airports, various visual and non-visual aids are located near runways, taxiways and aprons where they may present a hazard to aircraft in the event of accidental impact during landing, take-off or ground manoeuvring. All such equipment and their supports shall be frangible and mounted as low as possible to ensure that impact will not result in loss of control of the aircraft. This manual provides guidance on the design, testing and installation of frangible structures at airports and heliports. Much of the material is closely associated with the specifications on frangibility of visual and non-visual aids contained in Annex 14 — Aerodromes, Volume I — Aerodrome Design and Operations and Volume II — Heliports.