This guidance is provided to assist transportation planners and environmental practitioners in the use of corridor and subarea planning to inform the National Environmental Policy Act (NEPA) review process. This document responds to the need for additional guidance on how best to use corridor and subarea planning to bridge the transportation planning and NEPA processes as described in Appendix A to 23 Code of Federal Regulations (CFR) Part 450 - Linking the Transportation Planning and NEPA Processes.