Most of the solutions tested for traffic control have either been active RFID systems that leverage existing toll-collection tags, or longer-range, semi-passive tags. I am unaware of any passive ultrahigh-frequency (UHF) systems being used on public roads.
Adani Grain Logistics, which operates several grain-storage facilities in India, has implemented an automated, RFID-based system for receiving, testing and tracking food grain harvested within the states of Haryana and Punjab. The system, tested in April 2007, was deployed permanently three months later at two grain depots, located in the cities of Kaithal and Moga. Both depots are new, and are owned and operated by Adani.
The solution employs passive RFID tags to activate traffic lights at two grain depots that the firm operates (see RFID Facilitates Grain Storage in India). When a tag is interrogated, the system sends a message through the reader’s input-output port in order to trigger the light signal.
The active systems receive input from toll-collection tags and determine the speed and direction of traffic. That data is then used by existing traffic-management systems to optimize the timing of red and green signals in both directions.
—Mark Roberti, Founder and Editor, RFID Journal
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