In April 2009, the U.S. government unveiled its blueprint for a national network of high-speed passenger rail (HSR) lines, aimed at reducing traffic congestion, cutting national dependence on foreign oil, and improving rural and urban environments. In implementing such a project, it is essential to identify the factors that might influence decision making and the eventual success of the HSR project, as well as to foresee the obstacles that must be overcome. The authors review, summarize, and analyze the most important HSR projects carried out to date around the globe, focusing on the main concerns of HSR projects: their impact on mobility, the environment, the economy, and urban centers. The authors identify lessons for policy makers and managers who are implementing HSR projects.