Automatic vehicle identification (AVI) was first introduced in the United States in the 1960s and 1970s. However, in spite of several successful tests, AVI systems were not widely implemented. Now there is a resurgence of interest in AVI, both because of recent technological advances and because of the important role that AVI plays in integrated intelligent vehicle highway systems (IVHS). This paper reviews different AVI technologies and their functional capabilities. In particular, it describes different generic AVI systems, their characteristics, and how AVI technology can be and has been applied to toll/revenue collection, access control, surveillance, and fleet management.