Recent advances in economic analysis of the relationship between highway capital stock and economic performance provide important empirical assessments of the contribution of our nationís highways to economic growth. The focus of this project is to improve measures of highway capital stock, and thus further refine economic analysis of the stockís contribution to economic growth. This report summarizes project efforts. Chapter I describes the basis for productive highway capital stock measures. Section I of Chapter I describes the methodology and relevant capital stocks concepts. Section II describes existing highway and other public capital stock studies and the methodologies employed. Chapter II details recommendations for construction of a quality adjusted public capital stock. These recommendations were presented to the projectís Select Advisory Committee (SAC) for comments on December 10, 1997. Chapter III lists recommendations for future work. These recommendations were presented to the SAC for comments on October 27, 1998. Also at this meeting, methodologies employed in the construction of the highway capital stocks were described, the Fraumeni highway capital stock series was presented, and comparisons were made with other highway capital stock estimates. Finally, Chapter IV details the construction of the stocks to facilitate updates by FHWA and the adoption of relevant assumptions and methodologies by other researchers.