This work presents a low-cost stereo vision system aimed to the real-time detection of generic obstacles (without constraints on symmetry or shape) on the path of a mobile road vehicle. Thanks to a geometrical transform the perspective effect is removed from both left and right stereo images. The difference between the results is used for the detection of free-space in fr ont of the vehicle. The output of the processing is displayed on both an on-board monitor and a control-panel to give a visual feedback to the driver. The system was tested on MOB-LAB experimental land vehicle, which was driven for more than 3000~km along extra-urban roads and freeways at speeds up to 80~km/h, and demonstrated its robustness with respect to shadows and changing illumination conditions, different road textures, and vehicle movement.