The ACN-PCN system of rating airport pavements is designated by the International Civil Aviation Organization (ICAO) as the only approved method for reporting strength.
“The bearing strength of a pavement intended for aircraft of apron (ramp) mass greater than 5700 kg shall be made available using the aircraft classification number - pavement classification number ACN-PCN method………” (ICAO Annex 14, clause 2.6.2)
The ICAO system for civil airport pavements involves comparison of
an airport’s Pavement Classification Number (PCN) with an Aircraft
Classification Number (ACN). According to this world-wide ICAO
standard, aircraft can safely operate on a pavement if their ACN is
less than or equal to the pavement load bearing capacity or PCN. An
aircraft having an ACN equal to or less than the PCN can operate
without weight restrictions on a pavement. The PCN is formally
published in an Aeronautical Information Publication (AIP).