This paper presents theoretical basis and application of image analysis for propose of a vision-based driver assistance system that helps to drive and increase driving safety. Using a video stream from a camera observing at the road, a computer program generates approximated road geometry. Then the program uses algorithms to estimate road shape, road width and car position on the road. The image analysis also enhances evaluation of distance from the preceding car. The computer program could also generate graphical and sound alerts to warn the driver of too high speed of approaching the preceding car, too small distance to the left or right road edge and about road curvature ahead.