FIA
The Fédération Internationale de l'Automobile, founded in 1904, is the world governing body of motor sport. It issues the International Sporting Code and, for historic cars, Appendix K.
The FIA (Fédération Internationale de l'Automobile) is the world governing body of motor sport, based in Paris. It issues the International Sporting Code (ISC), under which all international competitions are run, making it the highest rule-making authority – from Formula 1 to historic rallying.
For classic-car events, Appendix K to the Sporting Code matters most: it governs which historic cars may start in which class and also sets out the framework for regularity rallies. The HTP and HRCP vehicle documents are issued to FIA specifications by the national sporting authorities (ASNs).
The FIA should not be confused with FIVA: the FIA is the motor sport federation, responsible for competition and regulations, whereas FIVA is the federation of historic vehicles, concerned with preservation and heritage. Many classic events are affiliated to one of the two – some to both.
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Related terms

FIVA
The Fédération Internationale des Véhicules Anciens, the worldwide federation of historic vehicles founded in 1966. It protects and promotes motoring heritage and is a non-governmental partner of UNESCO.
Appendix K
The FIA regulations for historic motor sport. They define vehicle classes and eligibility – and permit regularity rallies with an average speed of no more than 50 km/h.
ASN
A country's national sporting authority, recognised by the FIA. It grants licences and permits and issues the HTP and HRCP vehicle documents.