Autonomous Intelligent Vehicle Initiative (IVI) systems (which include in-vehicle forward- and side-looking sensors) can be supplemented by vehicle-vehicle and vehicle-highway cooperative and, if possible, passive elements to comprise a "sensor-friendly" highway environment that would enhance the operational efficiency, and ultimately, the safety benefits of emerging IVI driver-assist systems. Thus far in our research, we have identified the current limitations of autonomous sensing systems in target/background discrimination in dynamic and cluttered highway scenes. Based upon this, relatively inexpensive, passive vehicle-highway cooperative markings have been concepted to allow those limitations to be mitigated. Emphasis has been placed on 77 GHz (millimeter wave) and laser radar sensors - sensor bands which we believe will be used for products in the relatively near term. In this paper, we introduce relevant IVI systems, describe roadside signatures, and using the previous two sections as a basis, discuss various cooperative vehicle-highway concepts.