Vehicular communication is a hot topic for developing solutions for automatic guidance, safety-related problems, and end-user applications. The dedicated frequency band in Europe is around 5.9 GHz. Characterization of the communication channel is thus deeply studied especially for the urban and rural environments but most of the case studies are related to the prediction of path loss and fading distribution. In this paper, the special case of vehicular to infrastructure communication in a road tunnel is treated, owing to a ray tracing simulation tool. The influence of the direction of polarization of the field at the transmitter on channel characteristics is emphasized, assuming either an empty tunnel or the presence of a truck convoy. The contribution of the reflected waves on the trucks to the total field, the direction of departure and arrival of the rays, features of the polarization ellipse at the receiver, and cross-polarization discrimination are discussed.