It is expected that the Intelligent Transportation Systems (ITS) of the future will involve communication between vehicles and the roadside. In designing these communication systems it is imperative that one has a sound and detailed understanding of radio-wave propagation in both short-distance roadside and complicated urban environments. In this paper we discuss the type of propagation models that are needed for ITS designers to predict system performance. This paper has approached this problem by examining the radio-wave propagation in the roadway environment over the range of distances and at frequencies that will have the potential to meet the needs of ITS. The requirements of the individual functions of ITS were taken into consideration in addition to what portions of the radio frequency spectrum will be available.