Radio-frequency identification (RFID) is a technology that uses radio waves
to exchange data between a reader and an electronic tag attached to an object
for the purpose of identification and tracking. Figure 1.12 illustrates an
electronic toll collection (ETC) system which consists of: (1) a transponder
on the vehicle, (2) a tag reader antenna at each plaza toll lane, (3) lane controllers
that control the lane equipment and track vehicles passing through,
and (4) a host computer system. All of the toll plaza controllers are connected
to a central database. When a vehicle comes to the toll booth at a
speed, the tag reader detects the transponder and records the its unique ID,
the time instant, and other account-related information such as balance and
toll paid.