 One goal of automotive aerodynamics is to reduce the air turbulence, or drag, caused by the shape of the automobile.Aerodynamic drag may be reduced either by reduction of frontal area or by reduction of drag coefficient.In bodies such as automobiles and airships, drag decreases after the rear of a car's cross-sectional area is reduced to fifty percent of the car's maximum cross section; "the best position is nearer 45 per cent of the length, and ... to have this maximum cross- section nearer the rear end than the front, and its drag has proved even less".