The pulling device includes at least one motor; an epicyclic (or planetary) gear train comprising a first element, a second element, and a third element selected from an internal sun gear, an external ring gear, and a planet carrier, the first element being integrally secured in rotation with the output shaft of the motor, the second element being designed to drive an axle of the vehicle in rotation; the detection means detecting an anomaly with respect to the motor; the releasable locking means, that are capable of assuming a locking configuration locking the third element in rotation, and a release configuration for releasing the third element; and the control means command—controlling the maintaining of the locking means in the locking configuration when no anomaly is detected, and moving of the locking means into the release configuration when an anomaly is detected.