The interaction between a moving vehicle and a bridge was used by Yang and colleagues to develop an indirect method for determining bridge frequencies. In our current investigation, we have established an experiment to indirectly measure the frequency of a simply supported beam using a passing test vehicle. This approach also involves in-situ measurements, in which the vibrations of the bridge are recorded as the vehicle passes over it. Subsequently, the bridge frequencies can be obtained from the dynamic response of the mobile test vehicle. Based on this concept, our research has designed an experimental configuration in which a test vehicle travels along a bridge to measure the frequency of the structure. In the laboratory and in-situ experiments, the test vehicle was created as a system with a single degree of freedom (SDF), enabling vertical vibrations. In the laboratory it was guided by a system of tension cables that allowed the vehicle to move along the beam while staying in full contact with it. The presented experimental results demonstrate that the indirect bridge inspection method is applicable to frequency monitoring of bridges.