Constant Speed Aerodynamic Procedure for Heavy Vehicles


Develop and document an aerodynamic constant speed procedure for heavy vehicles that can accurately calculate the aerodynamic performance through the typical expected yaw angles during operation at highway speeds.


Recent and upcoming regulations in the United States and abroad have led to the development of various aerodynamic evaluations and data reduction for input into simulations models to predict greenhouse gas (GHG) emissions. Currently the United Stated Environmental Protection Agency (EPA) has published a modified SAE coast down procedure with an optional aerodynamic constant speed procedure trying to capture the aerodynamic and yaw performance of vehicles. European Commission (EC) is also working on an aerodynamic constant speed method to address the European Community Heavy Duty Vehicle (EU HDV) emissions. The technology being pursued is a constant speed test with a CDA normalized to zero wind conditions (CDA0) via a generic yaw curve for the vehicle class. A CDA versus vehicle speed profile is derived from the CDA0 and the generic yaw curve. This CDA versus vehicle speed curve will be used as input into the Greenhouse Gas Simulation. Japan is considering a similar standard. In order to lead globally, an aerodynamic constant speed method that can accurately capture the yaw performance of a heavy vehicle is desired.

  • SAE J 3156
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