An RFID system is used to detect whether an RFID tag is part of the load of a forklift or other transport device. In one aspect where the load is in motion relative to an RFID reader system, the RFID system obtains tag readings and derives tag vector motion information which can be compared to the known motion of the load to distinguish tags that are part of the load from false positives which are unavoidably also within the field of the reader system. A forklift antenna system may also make readings from load pickup to load deposit in a truck trailer, and utilize computed tag vector motion information to distinguish tags that are part of the load from false positives. The tag vector information my relate to tag velocity, tag acceleration, and/or rate of change of tag acceleration. The two components of the RFID system may communicate information on identified tags, and/or interact (e.g. by silencing tags), so as to cooperate in identifying true positive tags in the load. A portal or reader system location along the path of the forklift can be activated prior to arrival of the load to eliminate certain false positives from requiring evaluation while the forklift load is moving through the field region of such reader system. Vertical motion of the load can be utilized as a way of discriminating between true positive tags in the load and false positives.