To overcome the problem that a motor becomes a load if the motor is failed and locked since a stator of the motor is directly attached to an axle and a rotor of the motor is directly attached to a tire wheel or a brake drum in a constitution although there is an advantage that a drive train does not have a loss since the motor really looks like a drive wheel in the wheel-in motor embedded between the axle and a tire.

A clutch mechanism is constituted between the tire wheel or the brake drum and a rotor housing of the motor. A mechanism for coupling the tire wheel or the brake drum and the rotor housing is constituted when the motor is failed. The load is decoupled by decoupling the tire wheel or the brake drum and the rotor housing when the motor is failed.