Non-contact optical-based speedometers are widely used for many kinds of applications, ranging from vehicle driving dynamics tests to train speed measurements. The accuracy of these measuring instruments is maintained if they are periodically checked and calibrated according to the ISO 17025 standard. Nowadays, they are calibrated on tracks, mounting them on a vehicle, and comparing the speed measured by the device under calibration with that provided by a reference instrument. Even if this approach is valid, it is expensive, especially if very high speeds must be tested. Furthermore, the safety of the driver and technicians involved in the calibration process represents a non-negligible cost. Trying to overcome these limits, this paper proposes a novel test-bed for in-laboratory calibration of the optical-based speedometers even at very high speeds. The experimental results, reported in this paper, confirm the goodness of this proposal.