This synthesis will be of interest to designers, traffic engineers, planners, and others concerned with the collection and use of highway data. Information is presented on current practices of states in correlating or linking highway-related data maintained in various types of independent computer files. As computer technology has enabled data collection and storage to grow, data files have been developed independently in various units within highway agencies. This report of the Transportation Research Board describes the integrated highway information systems used by states to link independent data files so that the agency as a whole (as well as the individual units) will benefit from the ability to see and compare information from the various files.  The report for this topic can be purchased at https://www.trb.org/news/blurb_detail.asp?id=3424