In this work, we perform a path loss characterization of the vehicular-to-infrastructure (V2I) channel in an urban environment based on a log-distance path loss propagation model. The model parameters have been derived from channel measurements at 700 MHz and 5.9 GHz. The correlation between the path loss exponent and the height of the antenna used in the infrastructure side is investigated. The measurements have been collected in an urban area of Valencia, Spain, under real road traffic conditions.