Performance Evaluation of UHF RFID Technologies for Real-Time Passenger Recognition in Intelligent Public Transportation Systems

Automated passenger tracking in public transportation systems can be used to estimate the short-term demand and, thereby, to optimize the fleet schedule in real time. It can also be used to determine the origin-destination matrix and to maintain statistics of each passenger´s transportation habits over time, thus enabling enhancements in long-term planning. However, ubiquitously tracking passengers throughout a network requires the ability to recognize them at single locations in the network. In this paper, we study the merits of realizing this task by means of radio-frequency identification (RFID) technologies. Forty volunteers carried RFID tags of the norm EPC Gen2 in their backpacks, wallets, pockets, and hands through a mockup of a bus door equipped with four reading antennas. Setups with one and two rows of persons walking through the portal were evaluated. The RFID tags were embedded in laminated plastic cards. Single-tag cards embedded with a single EPC Gen2 tag and dual-tag cards that also contained a traditional Mifare tag were used. Recognition statistics of passengers for all the combinations of one, two, three, and four antennas are presented. The recognition percentages are mainly influenced by the antenna position and radiation pattern and by the line-of-sight conditions between the tag and the antennas.