The most well-known identification technologies used in tracking and tracing are bar codes and RFID (Radio Frequency Identification). Of these two, RFID is rapidly becoming more commonly used. Its advantages are the possibility to read/write in tags and the durability of the system in varying environmental conditions. RFID is more suitable for automated identification than bar codes are, as cargo units can be identified at longer distances, there is no need for visual contact, and the target can be mobile during identification. But tags that are inexpensive and readable at long distances are not yet available. The Auto-ID Centre is aiming to develop a tag priced at only 5 cents by the year 2005.