Autonomous driving assistance systems, methods, and programs acquire a planned travel route along which a host vehicle plans to travel and acquire map information including lane information about a road that is included in the planned travel route. The systems, methods, and programs acquire, from outside the host vehicle, obstacle information that includes a location of an obstacle on the road and that has been acquired by another vehicle that travels along the planned travel route ahead of the host vehicle, and generate, as assistance information that is used to perform autonomous driving assistance in the host vehicle that travels along the planned travel route, a travel trajectory candidate for the host vehicle based on the obstacle information and the lane information about the planned travel route.