In recent years, a number of new wind tunnels for the automotive industry have been built across the world, and more such facilities are planned for the near future. Many decisions made in the early planning phase of the wind tunnel shape the facility throughout its operating life and contribute to both the construction and operating costs of the wind tunnel. The intent of this paper is to outline that with an appropriate choice of the test section geometry of 3/4 open-jet wind tunnels. The flow interferences that occur due to the finite cross section of the jet in a conventional wind tunnel can be largely compensated for or reduced to a negligible extent. It is shown that for a wide range of vehicles with varying degrees of blockage, residual interference becomes surprisingly negligible, so that a correction of the measured quantities is not required and conditions of “free” air flow are generated in the test section. Furthermore, it is shown that the coarse dimensions of a test section can be much smaller than is often the case today without affecting the quality of the measurement results, which leads to lower construction costs, but above all to lower energy requirements for the operation of the system. It is shown that the instabilities of the free jet must also be assumed, which results in an upper limit for the jet length that should not be exceeded.