A computational study has been conducted to investigate the transient aerodynamic forces experienced by two vehicles overtaking each other. Ahmed body model has been used to represent the vehicles. The transient effects during the overtaking scenario have been determined by using a Computational Fluid Dynamics (CFD) model. This has been achieved by developing an open source computational code. The aerodynamic effects have been investigated by emulating this event in a virtual wind tunnel. One of the generic vehicles was set to be stationary, while the other was allowed to be moving at constant speed. The Delayed Detached Eddy simulation (DDES) turbulence approach has been applied in this study based on the finite volume analysis (FVA). The computational results such as fluid forces and moments acting on the vehicle structures have been compared against published experimental results. Encouraging correlations between those results are observed. In the present work, the fluid-structure interaction (FSI) phenomenon has also been studied by developing a flexible body dynamic model. The modal and dynamic responses are determined from FEM analysis by the application of fluid transient loads obtained from the CFD model. This investigation is important to address the issue of stability and performance of the vehicle system. This work provides a significant understanding into the complex aerodynamics of an overtaking process and gives the foundation for further analysis in the area of fluid-structure interactions for more complex geometries and scenarios.