A vehicle has a power system, in which an engine, a motor, a torque converter, a transmission, and an axle are connected in series. The transmission has a mechanism of varying a gear ratio under the control of a control unit. A driver of the vehicle operates a specific switch for setting a deceleration to specify a desired deceleration by means of power source braking. In response to an ON operation of a snow mode switch, a possible range of setting of the deceleration is restricted to a specific area that does not cause any slip or skid of the vehicle. The control unit totally controls the torque of the motor and the gear ratio, thereby implementing the braking at the desired deceleration. This arrangement attains the desired deceleration specified by the driver in the wide possible range of the setting, while restricting the deceleration to a specific range according to the driving conditions of the vehicle.