1. A system for recognizing a traffic lane marking line for a vehicle comprising: image photographing means for photographing a range including a road surface in a direction of travel of the vehicle; traffic lane marking line recognizing means configured to be capable of recognizing at least a traffic lane marking line in broken line on the road surface in a photographed image photographed by the image photographing means; image compositing means for compositing a plurality of images photographed at different time points by the image photographing means to elongate the traffic lane marking line in the photographed images; vehicle speed detecting means for detecting a travel speed of the vehicle; and image selecting means for selecting at least one image, among the plurality of images, photographed at a past time point earlier by a time interval determined in accordance with the vehicle speed detected by the vehicle speed detecting means from a reference time point, when defining a photographed time point of a given one of the images to be composited as the reference time point, as the image to be composited with the given one of the images.