SURROUNDINGS MONITORING SYSTEM AND PROGRAM

A surroundings monitoring system (30) is used with a system-mounted vehicle (40) equipped with an object sensor (21, 22) which senses an object around the system-mounted vehicle. When a vehicle approaching from behind the system-mounted vehicle on a road where the system-mounted vehicle is moving is detected by the object sensor, the surroundings monitoring system performs a collision avoidance task depending upon whether a predetermined warning condition for the approaching vehicle is met. The surroundings monitoring system determines whether a non-target vehicle is present in a region on the road which is defined to extend from the system-mounted vehicle to the approaching vehicle. The non-target vehicle is a vehicle not meeting the warning condition. When the non-target vehicle is determined to be present, the surrounding monitoring system inhibits the collision avoidance task from being performed for the approaching vehicle present behind the non-target vehicle.