1. A road line detection method comprising: obtaining a first disparity map including one or more road regions and a corresponding V-disparity image, the V-disparity image being a lateral view of the first disparity map; sequentially detecting plural sequentially adjacent road surfaces by iteratively detecting road surfaces based on corresponding sloped line segments in the V-disparity image from a starting point where disparity and V-value is maximum, each road surface being formed by linear fitting a plurality of reliable points that do not form a vertical line and whose gray levels are greater than a threshold and disparities are less than the reliable points of previously detected road surfaces; for each of the detected road surfaces, obtaining a second disparity map; and detecting one or more road lines in the second disparity map.