Abstract: An aerodynamic forebody device is provided for use with a tractor-trailer combination vehicle to be installed on the front of the semi-trailer. By optimizing the inclination angle of the top surface of the aerodynamic forebody device, aerodynamic drag is minimized. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.