With increasing emphasis on sustainable infrastructure as a setting for sustainable development, two broad types of questions arise: when is a particular infrastructure project sustainable and how is its impact assessed? This paper presents a methodology, tested on two exurban town centers, for assessing the impact of sustainable infrastructure, using various assessment indicators found in existing literature and that fall within the triple bottom line approach (economic, environmental, social). Findings suggest that the method does yield useful information for gauging the impacts of sustainable infrastructure investment, and that the impacts are mostly consistent with the expected and desired outcomes of denser exurban development, increasingly diverse land-use mix, and compact circulation.