This is a proposal to reduce air drag for cars and trucks which is the primary reason for cars' poor gas mileage.  Even though cars are streamlined, the frontal area (height x width, ≈ 20 sq. ft.), pushes the air and uses more fuel to overcome.  The proposal is to draw air in at the front, and to expel it out the back to reduce the air drag to zero.

The air is pulled in around the hood, fenders, and windshield.  Fans force air through ducts under the floor, and above the headliner to the rear where it is pushed out the back, minimizing or neutralizing the drag.

Rather than forcing air simply to overcome frontal-area drag, the air flow in the ducts can be increased to compensate for friction in the engine and other parts.