Vehicle propulsive aerodynamic elements

A drag reducing system for a bluff body having a length and a height, the system comprising:

• an air vane hingedly couplable to a surface of the bluff body, the air vane having a body portion, a leading portion, a lateral portion, an upper surface, and a lower surface, the air vane configured to rotate from a first position, wherein the air vane is positioned adjacent to the surface, to a second position, wherein the air vane is positioned projecting at an angle away from the surface,
• wherein the leading portion is flared inward toward the surface in the first position to provide a force to bias the air vane toward the first position when the airflow along the surface is aligned with the length of the bluff body, wherein the lateral portion is flared away from the surface in the first position to provide a force to rotate the air vane from the first position toward the second position when the airflow along the surface has a directional component upward along the height of the bluff body.