This paper presents an investigation of tag antenna
performance in the scenario of a passive RFID tag placed on an
asphalt road and inquired by readers in vehicles. Three types
of antennas were chosen and their properties were studied for
various dielectric properties of the asphalt paving. Water on
the pavement (e.g. due to rainfall) was also taken into account,
with various layer thicknesses. Based on the results of numerical
experiments performed using the finite-difference time-domain
(FDTD) method we demonstrate how the communication range
between the tag and a reader varies depending on the materials
surrounding the tag and wave polarization.