The reliability of the 1993 AASHTO Pavement Design Guide design method is questionable. The guide is based on methods that have evolved from theAASHTO Road Test (1958–1961). Through a number of editions from the initial publication (1962), the interim guide (1974), and other later editions, minor changes and improvements have been published. Nonetheless, these later modifications have not materially altered the original methods, which are based on empirical regression techniques relating simple material characterizations, traffic characterization, and measures of performance. In addition, the current AASHTO Pavement Design Guide does not provide performance prediction of pavements.