A system based on passive stereo machine vision is conceptually explored as a new approach to the problem of obstacle warning/avoidance. Past systems considered for obstacle warning have included microwave (radar), acoustical, and active (lidar) visible/infrared methods. However passive stereo machine vision has distinct advantages over all of these, primarily because it provides more information for scene understanding algorithms than other types of systems. A new software package named ATOM™ (for Automatic TOpographic Mapper) would be capable of extracting ranges at distances of 500 ft. and greater with sufficient accuracy to determine closing velocities of obstacles. If the computation cycle time were as low as 0.5 sec, this would be adequate to warn a driver in sufficient time to come to a complete halt before hitting stationary obstacles on dry or wet roads. Although computation cycle time on an off-the-shelf parallel processing computer is estimated at approximately 22 seconds, a computation time of 0.5 seconds is expected to be possible in two years on new versions of the same computer.