Devices, methods, and programs for identifying radio communication devices in a subject vehicle perform a first search and second search for radio communication devices in a vicinity of an in-vehicle device and store addresses of the radio communication devices identified by the first search and the second search. The devices, methods, and programs compare the addresses of the radio communication devices searched by the second search with the addresses of the radio communication devices searched by the first search, and determine that a particular radio communication device is inside the subject vehicle if that particular radio communication device's address is identified by both the first search and the second search.