1. A vehicle driving environment recognition system comprising: imaging means for periodically forming an input image of a forward road ahead of a road vehicle; lateral position detecting means for detecting a lateral position of the vehicle relative to a road in accordance with the input image; image integrating means for transforming the input image into a transformed image in a road plane coordinate system by using the lateral position; and for producing an integral image by integrating the transformed image; and feature extracting means for extracting a characteristic region from the integral image.