a ratio change mechanism, which is provided between an engine and driving wheels and which transmits a rotational driving force from said engine to said driving wheels with a speed change, and

a forward/reverse switching mechanism, which is provided between said engine and said ratio change mechanism and which transmits said rotational driving force being received from said engine to said ratio change mechanism with a switching of rotational direction between for a forward drive and for a reverse drive; and

said forward/reverse switching mechanism comprising:

a planetary gear train, which includes a sun gear element, a carrier element and a ring gear element, said sun gear element being connected to said engine, and said ring gear element being connected to said ratio change mechanism,

a forward drive clutch, which connects said sun gear element and said ring gear element, so that the rotation received from said engine is output as is to said ratio change mechanism in said rotational direction for a forward drive, and

a reverse brake, which fixes said carrier element stationary, so that the rotation received from said engine is output to said ratio change mechanism with a speed reduction in said rotational direction for a reverse drive;

wherein:

while said reverse brake is in engagement, a speed ratio of said ratio change mechanism is changed for a speed increase to a predetermined ratio; and

while said reverse brake is in engagement, a torque input from said engine is controlled such that said driving wheels receive a torque in a same magnitude as they receive while said forward drive clutch, instead, is in engagement.