The last-mentioned standards were adopted primarily to save energy in the use of automobiles and light trucks. Compliance is based on the average performance of a manufacturer's fleet, and additional credit toward compliance is available to alternatively fuelled vehicles.
La conformité aux normes est fondée sur la performance moyenne de l'ensemble de modèles d'un fabricant et il est possible pour un constructeur d'acquérir des «crédits» en vendant des véhicules qui utilisent des carburants de substitution.