The Intelligent Transportation Systems (ITS) Joint Program Office (JPO) is placing increasing emphasis on transferring ITS technology from research to deployment, and on accelerating the rate of ITS technology adoption. As part of these efforts, the JPO has sponsored research studies intended to improve the state of knowledge regarding the underlying characteristics and factors for technology adoption and deployment. This report is the final deliverable from the most recent of these studies, the Longitudinal Study of Implementation: Decision Factors and Effects (started in January 2012). This final report documents the findings and key observations from all tasks of the Longitudinal Study of Implementation. The Longitudinal Study of Implementation builds upon a body of existing work related to decision factors influencing ITS adoption, growth, maintenance or decline within the public and private sectors. The Longitudinal Study uses an interview-based approach to further analyze decision factors among public sector transportation agencies and the trucking industry; interviews with connected vehicle technology representatives from the automotive industry to assess their perspectives on what is needed for the connected vehicle environment to be fully realized; a post-hoc set of studies reviewing deployments, costs, and benefits at early ITS deployment sites; and a workshop and analysis of how to present cost and benefit information in a way that best informs and influences decision-makers. Finally, based on a cross-cutting assessment of these findings, the study team suggests several major themes for the federal government to consider regarding next generation ITS and the connected vehicle environment.