a belt drive continuously variable transmission has a primary pulley operatively connected to an engine and a secondary pulley operatively connected to wheels of a motor vehicle , hydraulic cylinders for changing effective diameters of both pulleys , and a transmission ratio control valve for producing a primary pressure applied to the primary cylinder for controlling transmission ratio . an anti - lock brake system is provided on the vehicle . a deceleration of the vehicle is calculated based on vehicle speed . time from an end of operation of the antilock brake system until the vehicle stops is calculated based on the calculated deceleration and to the vehicle speed . furthermore , downshifting speed necessary to increase the actual transmission ratio to a maximum transmission ratio before the vehicle stops is calculated based on the calculated time until the vehicle stops and to the actual transmission ratio . in place of the transmission ratio changing speed , the calculated downshifting speed is used when the operation of the antilock brake system ends .