A distance-velocity predicting system has an illuminator for projecting a light beam for searching for an obstacle, and a plurality of position sensors spaced at a distance corresponding to a base line length. A minimum value of a distance component from the base line to an obstacle lying in a direction perpendicular to the base line, which is obtained from the light beam and the position sensors, or a value in the neighborhood of the minimum value, is sampled to obtain time-series data, and a relative velocity component in a direction perpendicular to the base line with respect to the obstacle is obtained in real time by using the time-series data. The relative velocity component perpendicular to the base line is compared with a predetermined threshold value, and when the relative velocity component exceeds the threshold value, a starting signal for life protecting equipment is generated.