South Carolina State Highway Dept. v. Barnwell Brothers, Inc.

Mr. Justice STONE delivered the opinion of the Court. Act No. 259 of the General Assembly of South Carolina, of April 28, 1933, prohibits use on the state highways of motor trucks and 'semi-trailer motor trucks' whose width exceeds 90 inches, and whose weight including load exceeds 20,000 pounds. For purposes of the weight limitation, section 2 of the statute provides that a semitrailer motortruck, which is a motor propelled truck with a trailer whose front end is designed to be attached to and supported by the truck, shall be considered a single unit. The principal question for decision is whether these prohibitions impose an unconstitutional burden upon interstate commerce.

South Carolina has built its highways and owns and maintains them. It has received from the federal government, in aid of its highway improvements, money grants which have been expended upon the highways to which the injunction applies. But appellees do not challenge here the ruling of the District Court that Congress has not undertaken to regulate the weight and size of motor vehicles in interstate motor traffic and has left undisturbed whatever authority in that regard the states have retained under the Constitution.

While the constitutional grant to Congress of power to regulate interstate commerce has been held to operate of its own force to curtail state power in some measure, it did not forestall all state action affecting interstate commerce. Notwithstanding the commerce clause, such regulation in the absence of congressional action has for the most part been left to the states by the decisions of this Court, subject to the other applicable constitutional restraints.

The commerce clause by its own force, prohibits discrimination against interstate commerce, whatever its form or method, and the decisions of this Court have recognized that there is scope for its like operation when state legislation nominally of local concern is in point of fact aimed at interstate commerce, or by its necessary operation is a means of gaining a local benefit by throwing the attendant burdens on those without the state. It was to end these practices that the commerce clause was adopted. The commerce clause has also been thought to set its own limitation upon state control of interstate rail carriers so as to preclude the subordination of the efficiency and convenience of interstate traffic to local service requirements.

But the present case affords no occasion for saying that the bare possession of power by Congress to regulate the interstate traffic forces the states to conform to standards which Congress might, but has not adopted, or curtails their power to take measures to insure the safety and conservation of their highways which may be applied to like traffic moving intrastate. Few subjects of state regulation are so peculiarly of local concern as is the use of state highways. There are few, local regulation of which is so inseparable from a substantial effect on interstate commerce. Unlike the railroads, local highways are built, owned, and maintained by the state or its municipal subdivisions. The state has a primary and immediate concern in their safe and economical administration. The present regulations, or any others of like purpose, if they are to accomplish their end, must be applied alike to interstate and intrastate traffic both moving in large volume over the highways. The fact that they affect alike shippers in interstate and intrastate commerce in large number within as well as without the state is a safeguard against their abuse.

The nature of the authority of the state over its own highways has often been pointed out by this Court. It may not, under the guise of regulation, discriminate against interstate commerce. But, 'In the absence of national legislation especially covering the subject of interstate commerce, the state may rightly prescribe uniform regulations adapted to promote safety upon its highways and the conservation of their use, applicable alike to vehicles moving in interstate commerce and those of its own citizens.' This Court has often sustained the exercise of that power, although it has burdened or impeded interstate commerce. It has upheld weight limitations lower than those presently imposed, applied alike to motor traffic moving interstate and intrastate. Restrictions favoring passenger traffic over the carriage of interstate merchandise by truck have been similarly sustained.

In each of these cases regulation involves a burden on interstate commerce. But so long as the state action does not discriminate, the burden is one which the Constitution permits because it is an inseparable incident of the exercise of a legislative authority, which, under the Constitution, has been left to the states.

Congress, in the exercise of its plenary power to regulate interstate commerce, may determine whether the burdens imposed on it by state regulation, otherwise permissible, are too great, and may, by legislation designed to secure uniformity or in other respects to protect the national interest in the commerce, curtail to some extent the state's regulatory power. But that is a legislative, not a judicial, function, to be performed in the light of the congressional judgment of what is appropriate regulation of interstate commerce, and the extent to which, in that field, state power and local interests should be required to yield to the national authority and interest. In the absence of such legislation the judicial function, under the commerce clause, as well as the Fourteenth Amendment, stops with the inquiry whether the state Legislature in adopting regulations such as the present has acted within its province, and whether the means of regulation chosen are reasonably adapted to the end sought.

Here the first inquiry has already been resolved by our decisions that a state may impose nondiscriminatory restrictions with respect to the character of motor vehicles moving in interstate commerce as a safety measure and as a means of securing the economical use of its highways. In resolving the second, courts do not sit as Legislatures, either state or national. They cannot act as Congress does when, after weighing all the conflicting interests, state and national, it determines when and how much the state regulatory power shall yield to the larger interests of a national commerce. And in reviewing a state highway regulation where Congress has not acted, a court is not called upon, as are state Legislatures, to determine what, in its judgment, is the most suitable restriction to be applied of those that are possible, or to choose that one which in its opinion is best adapted to all the diverse interests affected.

Since the adoption of one weight or width regulation, rather than another, is a legislative, not a judicial, choice, its constitutionality is not to be determined by weighing in the judicial scales the merits of the legislative choice and rejecting it if the weight of evidence presented in court appears to favor a different standard. The choice of a weight limitation based on convenience of application and consequent lack of need for rigid supervisory enforcement is for the Legislature, and we cannot say that its preference for the one over the other is in any sense arbitrary or unreasonable. The choice is not to be condemned because the Legislature prefers a workable standard, less likely to be violated than another under which the violations will probably be increased but more easily detected. It is for the Legislature to say whether the one test or the other will in practical operation better protect the highways from the risk of excessive loads.

The regulatory measures taken by South Carolina are within its legislative power. They do not infringe the Fourteenth Amendment, and the resulting burden on interstate commerce is not forbidden.