With the advent of automatic vehicle identification (AVI) systems, there has been an increased concern on the part of state and public agencies implementing AVI technology relative to the issue of public and worker exposure to the associated RF fields. In a project conducted for the Triborough Bridge and Tunnel Authority (TBTA) in New York, RF field measurements were made to determine the intensity of the fields at the toll booth, inside moving vehicles (automobiles and buses) and in the immediate vicinity of the transmitting antenna systems. This photo shows a test system located in Dallas, Texas where moving vehicle measurements were made with the antenna (with the yellow circle) oriented to expose a transponder tag placed just inside the vehicle's front window.
AVI antennas are often mounted from above and directed toward the oncoming traffic stream. This photo shows measurements being performed in New Jersey to assess the variation of RF field strengths with distance from the antenna that is mounted beneath a bridge over the tollway.
