Considerable amounts of the everyday goods transports are done using light trucks. In the last ten years (2005-2015), the number of light trucks has increased by 33 % in Sweden. The majority of these light trucks are fitted with a swap body and encounter the same problem as many other truck configurations, namely that several different manufacturers contribute to the final shape of the vehicle. Due to this, the aerodynamics of the final vehicle is often not fully considered. Hence there appears to be room for improving the aerodynamic performance. In this study the flow around a swap body fitted to a light truck has been investigated using Computational Fluid Dynamics. The focus has been on improving the shape of the swap body in order to reduce both the aerodynamic drag and fuel consumption, while still keeping it usable for daily operations. Reynolds-Averaged Navier-Stokes simulations were used for concept evaluation while more advanced Detached Eddy Simulations were performed on the best concept in order to investigate details of the flow. Various concepts were evaluated from which it could be seen that a more streamlined top of the swap body together with a lowered top trailing edge had a significant positive effect on the aerodynamic drag. A full scale light truck was equipped with a swap body with with these modifications for road tests. During a test period, a mean fuel consumption reduction of 12 % was measured, thus indicating a significantly reduced aerodynamic drag.