The TRB Committee for a Review of U.S. Department of Transportation (U.S. DOT) Study on Implementation of Changes to the Section 4(f) Process has delivered a letter report to the Honorable Mary E. Peters, Secretary of the U.S. DOT. Legal rulings and regulations pursuant to Section 4(f) of U.S. Department of Transportation Act of 1966 set high standards for protecting parks, recreation areas, wildlife refuges, and historic properties from being adversely affected by transportation projects. The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users requires the U.S. DOT to streamline the Section 4(f) evaluation process and to study the consequences of these regulatory changes. Congress also required that a TRB committee evaluate the design and outcomes of the U.S. DOT studies. In its first letter report, the committee finds that given the lack of baseline data and the qualitative nature of the issues under study, a truly experimental study design is not possible. Nonetheless, the committee makes several suggestions for how the proposed study design can be strengthened to allow reasonable inferences to be drawn.