Method and apparatus for judging road surface conditions

A method for judging road surface conditions, comprising the steps of: detecting rotational information of tires; storing the rotational information of the respective tires; calculating a vehicle velocity; calculating an acceleration/deceleration of the vehicle; calculating a slip ratio of left-sided front and rear wheels and right-sided front and rear wheels and a slip ratio of front and rear wheels, respectively; calculating an amount of fluctuation in differences in slip ratios between the right and left wheels; obtaining a linear regression coefficient and a correlation coefficient between the slip ratio of the front and rear wheels and the acceleration/deceleration of the vehicle; and setting a threshold for judging road surface conditions.