In all kinds of shapes and form road vehicles use up energy in the form of fuel. It is interesting to note that on the highway more than half of the useful energy output of the engine is used to accelerate and heat the surrounding air molecules. Aerodynamic drag is the aerodynamic force that opposes motion and accounts for a large fraction of transportation energy consumption. The main objective of this paper is to provide a solution to reduce the aerodynamic drag of road vehicle. This is achieved by modifying the design of vehicle by attaching a tailgate to the end of the trailer and then verifying mathematically whether the modification has any effect in reducing drag. Idealized vehicle geometry has been used. In this study, a numerical fluid mechanics study has been carried out extending the tailgate on one side as well as on both sides. The angle of the tailgate is changed to study the influence of the tailgate angle on the drag of the trailer. Computations were carried out with and without ground effects. It was observed that drag coefficient reduced as tailgate angle is increased upto 250 and after that the drag starts increasing reducing the benefit.