A tractor-trailer system uses aerodynamic principles to use crosswind to its advantage. The system has a curvilinear duct by having a attaching a convex body on the trailer front and a concave body on the back of the cab. When a cross wind enters the gap, it creates a negative pressure (compare to ambient) on the convex surface (trailer front) and a positive pressure on concave surface (back of the cab). Both of these pressures will help reduce the drag. Further having the crosswind flow smoothly can lead to less turbulence intensity in the gap, which can help in improving handling qualities of the system. There is a similar situation both for drag as well as handling qualities can be given for the air traveling in vertical direction (even at zero cross wind).