This SAE J2971 Recommended Practice Truck and Bus Aerodynamic Device Terminology document describes a standard naming convention of aerodynamic devices and technologies used to control aerodynamic forces on truck and buses weighing more than 10@000 pounds (including trailers). Purpose This recommended practice provides a detailed list and definition of truck and bus aerodynamic device terminology that may provide a common nomenclature for use in publishing data@ reports and SAE recommended practices. Document Use This document is structured to service both the novice and the expert user.