In American Trucking Ass'ns v. United States, 364 U.S. 1, 6, 80 S.Ct. 1570, 1574, 4 L.Ed.2d 1527 (1960), "the critical issue raised ... was whether the Commission exceeded its statutory authority by granting the permits in question to a railroad subsidiary without imposing more stringent limitations than it did." Finding that "both the Commission and this Court have recognized that Congress has expressed a strong general policy against railroad invasion of the motor field," the Court reversed the Commission's grant of unrestricted authority to a rail-affiliated carrier where the Commission had not found sufficient special circumstances to justify the grant. Id. The Court noted that "the Commission long ago concluded that the policy of the transportation legislation requires that the standards of the acquisitions section be followed as a general rule in other situations, notably in applications for common carrier certificates of convenience and necessity." Id. The Court further stated that "the policy of opposition to railroad incursions into the field of motor carrier service ... has not been implemented merely by way of a more or less unguided suspicion of railroad subsidiaries, but rather has evolved through a series of Commission decisions from embryonic form into a set of reasonably firm, concrete standards." Id. at 7, 80 S.Ct. at 1574.