In American Trucking Ass'n v. Atchison, Topeka & S.F. Ry. Co., 387 U.S. 397, 87 S.Ct. 1608, 18 L.Ed.2d 847 (1967), the Supreme Court upheld the authority of the Interstate Commerce Commission to alter an interpretation of a statute that it had followed for some twenty-five years on the ground that it had decided that interpretation was incorrect. The Court remarked that an agency "faced with new developments or in light of reconsideration of the relevant facts and its mandate, may alter its past interpretation and overturn past administrative rulings and practice." (387 U.S. at 416, 87 S.Ct. at 1618.) In American Trucking Ass'n, Inc. v. Atchison Topeka & Santa Fe Ry. Co., 387 U.S. 397, 416, 87 S.Ct. 1608, 1618-19, 18 L.Ed.2d 847 (1967), the Supreme Court stated: the Commission, faced with new developments or in light of reconsideration of the relevant facts and its mandate, may alter its past interpretation and overturn past administrative rulings and practice. . Regulatory agencies do not establish rules of conduct to last forever; they are supposed, within the limits of the law and of fair and prudent administration, to adapt their rules and practices to the Nation's needs in a volatile, changing economy. In American Trucking Ass'ns v. Atchison, Topeka & Santa Fe Ry. Co., 387 U.S. 397, 416, 87 S.Ct. 1608, 1618, 18 L.Ed.2d 847 (1967), the Supreme Court reasoned as follows: The Commission, faced with new developments or in light of reconsideration of the relevant facts and its mandate, may alter its past interpretation and overturn past administrative rulings and practice. Compare SEC v. Chenery Corp., 333 U.S. 194 (1947); FCC v. WOKO, 329 U.S. 223 67 S.Ct. 213, 91 L.Ed. 204 (1946). In fact, although we make no judgment as to the policy aspects of the Commission's action, this kind of flexibility and adaptability to changing needs and patterns of transportation is an essential part of the office of a regulatory agency. Regulatory agencies do not establish rules of conduct to last forever; they are supposed, within the limits of the law and of fair and prudent administration, to adapt their rules and practices to the Nation's needs in a volatile, changing economy. They are neither required nor supposed to regulate the present and the future within the inflexible limits of yesterday. (Id. at 416, 87 S.Ct. 1618.)