1. A vehicle control system, comprising: an imaging unit that performs stereo-imaging by a pair of cameras that capture an advance direction of a vehicle equipped with the cameras; and an image processor that performs image processing for recognizing a vehicle exterior environment, on the basis of a captured image obtained by the imaging unit, wherein the image processor executes: a distance calculation process of detecting, by pattern matching, corresponding points between a pair of captured images obtained through the stereo-imaging, working out a coordinate shift between the corresponding points as a parallax, and calculating a distance up to each corresponding point, on the basis of the parallax; a representative distance calculation process of dividing a distance image, in which a distance of each corresponding point as calculated in the distance calculation process is represented on an image, into a plurality of strip regions that partition the distance image in a vertical direction, and working out, for each strip region, a distance for which a frequency is equal to or higher than a predefined value as a representative distance; and a determination process of counting a number of the representative distances within a monitoring region that is set at a horizontal center section of a bottom end of an image having the distance as a vertical axis and having an image left-right position of the captured image as a horizontal axis, and determining a magnitude relationship between the count value and a threshold value.