1. A cruise control system for an automotive vehicle, for controlling cruising of own vehicle with maintaining a distance to a preceding vehicle constant, comprising: traffic signal characteristics obtaining means for obtaining characteristics of a traffic signal ahead; road information obtaining means for obtaining intersection information including a distance to an intersection; intersection arrival time calculating means for calculating arrival timing of the own vehicle and the preceding vehicle on the basis of a distance to the intersection, an own vehicle speed and a preceding vehicle traveling condition; traffic signal condition estimating means for estimating said condition of the traffic signal on the basis of the traffic signal characteristics and said intersection arriving time; and control content modifying means for modifying a content of cruise control of the own vehicle depending upon said estimated traffic signal condition.