U.S. Department of Transportation study that reviews and evaluates technology development opportunities, equipment upgrades, and best practices of rail industry segments for improving energy efficiency performance and attaining environmental sustainability goals. This report presents data on comparative rail energy efficiency, emerging energy efficient technologies, and alternative fuels. Based on a comprehensive literature review and on experts’ inputs, the report presents model corporate sustainability plans, rail equipment upgrade opportunities, system-wide best practices, and success stories that measurably improved energy efficiency performance with environmental and economic benefits for all rail industry segments. Findings and recommendations are tailored to intercity and commuter passenger rail, as well as to freight rail carrier needs and goals for improved, but cost-effective, energy efficiency and environmental performance. Key opportunities include: public-private partnerships for R&D, demonstrations and equipment upgrades with Federal agencies, trade associations (AAR, APTA, AASHTO), international rail organizations (UIC), and regional and State environmental protection agencies for energy efficiency and cross-enterprise sustainability improvements.