In January 2006, the Massachusetts Highway Department issued a new Project Development and Design Guide that dramatically reshaped the way in which transportation projects were implemented throughout the commonwealth. The process and the resulting guide are outstanding examples of mainstreaming principles and objectives of context-sensitive design (CSD) into highway planning and design on a statewide level. This paper explores the history of CSD in Massachusetts, describes the process used to develop and implement the new guide, provides an overview of context-sensitive project development and design guidelines included in the guide, and identifies some conclusions and lessons learned from this experience.