Disclosed is a rig (1) for testing an automatic underground train (2), including at least two rolling units (8) at a distance from each other, each one provided for rolling at least one wheel (6) of the train (2) thereon, each unit (8) including: a rotary inertial body (28); a motor (26) engaged with the inertial body; and a sensor (51) for the rotational speed of the inertial body; the rig also including a unit (11, 15) for controlling each of the motors (26) so as to permanently eliminate any difference in speed between the rolling units.