route existed and that fact was deemed relevant, the duty to prove it rested upon the applicant. It was not incumbent upon the Commission to offer a certificate over an alternate route.
Second. It is contended that an order denying to a common carrier by motor a certificate to engage in interstate transportation necessarily violates the Commerce Clause. The argument is that under the rule declared in Buck v. Kuykendall, 267 U.S. 307 and Bush & Sons Co. v. Maloy, 267 U.S. 317, an interstate carrier .is entitled to a-certificate as of right; and that hence the reason for the commission’s.refusal and its purpose- are immaterial. In those cases, safety was doubtless promoted when' the certificate was denied, because intensification of traffic was thereby prevented. See Stephenson v. Binford, 287 U.S. 251, 269-272. But there, promotion of safety was merely an incident of the denial. Its purpose was to prevent competition deemed undesirable. The test employed was the adequacy of existing transportation facilities; and since the transportation in question was interstate, denial of the certificate invaded the. province of Congress. In the case at bar, the purpose of the denial was to promote safety; and the test employed was congestion of the highway. The effect of the denial upon interstate commerce was merely an incident.
Protection against accidents, as against crime, presents ordinarily a local problem. Regulation to ensure safety is an exercise of the police power. It is primarily a state function, whether the locus be private property or the public highways. .Congress has not dealt with the subject. Hence, even where the motor cars are used exclusively in interstate commerce, a State may freely exact registration of the vehicle and an operator’s license, Hendrick v. Maryland, 235 U.S. 610, 622; Clark v. Poor, 274 U. S. 554, 557; Sprout v. South Bend, 277 U.S. 163, 169; may require the appointment of an agent upon whom