Highway communication using wide-band cable and inductive transmission methods

Problems are discussed that are presented by shortage of available radio channels if conventional space-wave propagation modes are to be utilized on any extensive basis in establishing new communication and control facilities on interstate highways to enhance safety and efficiency of operation. The need for an integrated-system approach to attain maximum efficiency in the use of the radio spectrum, and adaptability to orderly expansion by compatible stages in accommodating future functions such as those involved in the automatic-highway concept are emphasized. A review of proposed highway communication, surveillance, and control functions, indicates future requirement for a very substantial bandwidth in the radio-frequency spectrum, as well as the need for localization and directionalization of signaling fields to minimize interference difficulties. Use of coaxial-cable systems, with roadside transmission facilities positioned below ground level, is proposed in lieu of microwave or other radio-relay techniques for a number of point-to-point communication and control functions of value to the public and to highway departments. The technical aspects of these roadway services, as well as factors relating to utilization of induction-radio transmission methods as a means of restricting effective signaling range substantially within the right-of-way for vehicular communication functions are discussed. Field strength and other measurement data as derived from experimental tests of roadside-cable systems at various carrier frequencies are incorporated.