This paper reviews and summarizes current literature by Theofanis P. Mamuneas (2008) and Mamuneas with M. Ishaq Nadiri (2003) on the returns to highway investments. This paper first provides an overview of the conceptual relationship between highways and output. The next section describes the highway capital stock estimated by Fraumeni and used by Mamuneas. Next, the paper describes the study conducted by Mamuneas and analyzes the results for consistency within the modeling framework and in context with other studies. The paper then briefly summarizes the broad range of estimates from the literature to offer additional context. Finally, the paper offers an overview of the issues that still need to be addressed to provide more definitive estimates.