In recent years, strategies to promote transportation and land use integration have gained prominence in planning-related fields, believed to yield many potential benefits toward travel, health, welfare, and sustainability goals. Although livability has been identified as an important outcome of this approach as well, little guidance exists on what livability actually is, how to measure it, or how transportation and land use integration strategies can promote it. The findings of a multiyear study of the livability literature, theory, and practice are followed by an extensive quantitative and qualitative study of more than 350 transit corridors including thousands of stations throughout the United States. Although often dismissed as subjective, this research shows that livability can be understood in well-defined and measurable ways, which are validated through an innovative geospatial approach using detailed national data on travel, health, safety, and other quality-of-life outcomes. The findings in this paper show how more integrated and livable transit corridors can yield multiple benefits regarding travel, health, welfare, and sustainability. The findings show how livability goals and their measures can inform planning decisions to promote equitable access to opportunities locally and regionally and yield multiple benefits. Therefore, livability can be seen as an organizing principle for determining when and how to deploy integrated transportation and land use planning strategies. A practical handbook and a calculator for building livable transit corridors are introduced; both were designed to empower practitioners and members of the public to equitably achieve higher levels of livability at local and regional scales.