PURPOSE: To make a fly-wheel (FW) generate exactly an overrun rotation when the angular deceleration of a prescribed value or above has been generated in a body to be tested, by constituting a one-way clutch which becomes a lock state when a driving shaft is in a driving side position against the FW.

CONSTITUTION: When a vehicle is running, a rotation of a forward direction of a front wheel is transferred to an input member 75 through a connecting ring 116, an elastic friction member 115, and a connecting flange 113 from a hub 8. Also, its speed is increased by a ring gear 76, planetary gears 781, 782, and a sun gear 79 and it is transferred to an output shaft 42. Also, a one-way clutch 83 is set to a lock state, and said rotation is transferred to an FW 72 through a clutch 83, a transmission wheel 84, and a cam mechanism 73 successively and drives this FW, therefore, the FW 72 rotates at a higher speed than the front wheel. Accordingly, the FW 72 has a large rotational inertia force. At the same time, a cam shaft 26 and a speed meter 51 are also driven by a rotation of the gear 781. When an excess load is applied to an angular deceleration sensor 21 in the course of driving, a slide is generated in one of the connecting ring 116, the member 115, and the flange 113, a transfer torque to the member 75 from the hub 8 is suppressed, and an action of the excess load to the sensor 21 is avoided.