Abstract: In the vehicle using the three-channel anti-lock control method based on the front wheel independent-and-rear wheel select-low, only when the third system speed Vs3 to which the left and right rear wheels belong is subjected to the anti-lock control due to the abruptly decreasing of the third system speed before at least one of the left and right front wheel systems begin to be subjected to the anti-lock control, the decrease of the brake hydraulic pressure is not started even if the third system speed Vs3 becomes lower than the above threshold speed VT1 (Vs3<VT1). In such case, only when the third system speed Vs3 becomes equal to or lower than the reference speed Vr (Vs3.ltoreq.Vr), the decrease of the hydraulic pressure is started. By doing so, an excessive decrease of the brake hydraulic pressure in the third system at the time of the braking during the turning of the vehicle is prevented.

Abstract: An anti-lock control apparatus and method in which the brake hydraulic pressure is controlled by regarding an estimated vehicle speed as an actual vehicle speed, is characterized in that the estimated vehicle speed is corrected when the estimated vehicle speed is extremely reduced relative to the actual vehicle speed when the four wheel speeds are reduced at the same time, or the like, thereby preventing the estimated vehicle speed from being away from the actual speed. It can be applied as the correction of the estimated vehicle speed that the estimated vehicle speed may be maintained at a constant value, and the deceleration and acceleration of the estimated vehicle speed may be varied in accordance with a friction coefficient of the road surface.