dissenting:
We take a different view. Measured by the oft-repeated judicial rule that every enactment of a legislature carries a presumption of constitutional validity, the Arkansas tax has not,, in our opinion, been shown to be beyond all reasonable doubt in violation of the constitutional provision that “Congress shall have power to . . . regulate commerce . . . among the States.” “In case of real doubt, a law must be sustained.” Mr. Justice Holmes in Interstate Consolidated Ry. Co. v. Massachusetts, 207 U. S. 79, 88.1 Congress, sole constitutional legislative repository of power over that commerce, has *184enacted no regulation prohibiting Arkansas from levying a tax — on gasoline in excess of twenty gallons brought into the State — in return for the use of its highways. Gasoline taxes are widely utilized for building and maintaining public roads, and the proceeds of this Arkansas tax are pledged to that end. Arkansas can levy a gallon-age tax on any gasoline withdrawn from storage within the State and placed in the tanks of this carrier's vehicles “notwithstanding that its ultimate function is to generate motive power for carrying on interstate commerce.” Edelman v. Boeing Air Transport, 289 U. S. 249, 252. The present tax aims at carriers who would escape such taxation, unless we are to require Arkansas to shape its taxes to the circumstances of each carrier.
The cost entailed by the construction and maintenance of modern highways creates for the forty-eight States one of their largest financial problems. A major phase of this problem is the proper apportionment of the financial burden between those who use a State’s highways for transportation within its borders and those who do so in the course of interstate transportation. Striking a fair balance involves incalculable. variants and therefore is beset, with perplexities. The making of these exacting adjustments is the business of legislation — that of state legislatures and of Congress. This Court has but a limited responsibility in that state legislation may here be challenged if it discriminates against interstate commerce or is hostile to the congressional grant of authority. McGoldrick v. Berwind-White Coal Mining Co., ante, p. 33.
Arkansas’ tax hits the big, heavy busses and trucks which, it is well established, entail most serious wear and tear upon roads. Had Arkansas expressly declared the challenged statute to be a means, of working out a fair charge upon-these heavy vehicles for cost and maintenance of the roads they travel in the State, the relation*185ship between the means employed and these allowable ends — however crude and awkward — would have been rendered more explicit, but not made more evidently a matter of policy and administration,; and therefore not for judicial determination. Certainly, the State had power to impose flat fees or taxes graduated according to gasoline used, horsepower, weight and capacity or mileage, and yet those taxes would not measure with exact precision the taxpayers’ use of Arkansas highways.2 It is not for us to measure the refinements of fiscal duties which a State may' exact from these heavy motor vehicles.3
This case again illustrates-the wisdom of the Founders in placing interstate commerce under the protection of Congress. The present problem is not limited to Arkansas, but is of national moment. Maintenance of open channels of trade between the States was not only of paramount importance when our Constitution was framed; it remains today a Complex problem calling for national vigilance and regulation.
Our disagreement with the opinions just announced does not arise i;rom a belief that federal action is unnecessary to bring about appropriate uniformity in regulations of interstate commerce. Indeed, state legislation recently before" this Court indicates quite the contrary. For instance, we sustained the right of South Carolina— *186in the absence of congressional prohibition — to regulate the width and weight of interstate trucks using her highways, even though the unassailed findings showed that a substantial amount of interstate commerce would' thereby be barred from the State. South Carolina Highway, Dept. v. Barnwell Bros.4 We did not thereby approve the desirability of such state regulations. It is not for us to approve or disapprove. We did decide that “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 national commerce.”5 As both the Union and the States are more and more dependent upon the exercise of their taxing powers for carrying on government, it becomes more and more important that potential conflicts between state and national powers should not be found where Congress has not found them, unless conflict is established by demonstrable concreteness. See Hammond v. Schappi Bus Line, 275 U. S. 164.
Even under the principle enunciated by the majority— that Arkansas may not measure her tax by gasoline carried in appellee's tanks for usé in other States — ithe challenged judgment should not stand.
Arkansas admittedly has power to .tax appellee upon'" gasoline used within her borders, and need not, of course, extend to appellee any exemption for a reserve. The record discloses that appellee's busses travel 1188.8 miles each day over Arkansas highways. The trial judge found, and there is evidence to support the finding, that these busses use about one gallon of gasoline for every five miles traveled. Thus, appellee uses about 237.76 gallons *187of gasoline a day in Arkansas, upon which the tax of 6.5 cents per gallon used would amount to $15.45 a day.
Appellee’s busses travel four different routes, two from Memphis through Arkansas to Missouri, and two from Memphis to cities in Arkansas. On the trips to Missouri the tax now exacted by Arkansas is greater than would be a tax on the gasoline actually used in Arkansas. But on the trips from Memphis into Arkansas and back, the tax exacted, because of the 20-gallon exemption, is less than would be a tax on the gasoline used in Arkansas.
As appellant points out in his brief, when all the routes are taken together, the daily tax which Arkansas would collect if appellee carried only enough gasoline to complete each trip would only amount to $13.00 — actually $2.45 less than a tax on gasoline consumed in Arkansas.
This amount — $2.45—eqpa-ls the present tax on 37 gallons of gasoline. Appellee’s busses enter Arkansas 13 times each day. It follows that appellee may carry a reserve of almost three gallons on each trip and still pay no more than the tax which, as the majority assumes, Arkansas could constitutionally impose on the gasoline actually consumed on- her own roads. There is nothing in the record to show that a greater reserve is necessary. An interstate carrier has no absolute right to -fix the size and character of its equipment used in interstate commerce, in total disregard of the necessities of the enterprise and the requirements of States through which the carrier operates.6 Exactions by such States may well be designed to operate upon the quantity of gasoline reserves for considerations analogous to those which have called into being state regulations of the size, weight and number of the vehicles themselves. And a state tax which may induce a reduction in the amount of reserve previously *188carried is no more to be condemned on that sole ground alone, than is a state law actually prohibiting vehicles above a certain size or weight. That this reduction may be attributable to a tax rather than to a regulatory measure expressly passed in the interests of public safety should not be controlling. Particularly is this so when the proceeds of the tax are utilized exclusively for highway purposes and the tax itself is directed to gasoline used, just as other equipment is used, in the course of interstate business and involves no manifestation of hostility to — or levy upon — gasoline carried as a commodity in interstate commerce. It is presumably safe to rely on appellee’s self-interest to work out any schedules of refueling at its various storage facilities necessitated by changes in reserves carried.- We cannot believe that ap-pellee is able to attack the constitutionality of this tax on the ground that as to others it might operate differently and serve to burden the use of gasoline in other States.7 It is important to bear in mind that we are not passing upon a statute as such but upon the incidence of this statute in the single concrete situation presented by a. specific objector on this specific record. The very‘fact that such niceties of calculation have to be indulged in as the concurring opinion finds necessary in order to establish the mischief of'the statute, makes manifest the “real doubt” of any showing of unconstitutionality and indicates that a burden of calculation and speculation is assumed in the exercise of the judicial 'function which should be left to the legislatures of the States and the Congress.
Judicial control of national commerce — unlike legislative regulations — must from inherent limitations of the judi*189cial process treat the subject by the hit-and-miss method of deciding single local controversies upon evidence and information limited by the narrow rules of litigation. Spasmodic and unrelated instances of litigation cannot afford an adequate basis for the creation of. integrated national rules which alone can afford that full protection for interstate commerce intended by the Constitution. We would, therefore, leave the questions raised by the Arkansas tax for consideration of Congress in a nation-wide survey of the constantly increasing barriers to trade among the States. Unconfined by “the narrow scope of judicial proceedings”8 Congress alone can, in the exercise of its plenary constitutional control over interstate commerce, not only consider whether such a tax as now under scrutiny is consistent with the best interests of our national economy, but can also on the basis of full exploration of the many aspects of a complicated problem devise a national policy fair alike to the States and our Union. Diverse and interacting state laws may well have created avoidable hardships. See, Comparative Charts of State Statutes illustrating Barriers to Trade between States, Works Progress Administration, May, 1939; Proceedings,The National Conference on Interstate Trade Barriers, The Council of State Governments, 1939. But the remedy, if any is called for, we think is within the ample reach of Congress.
Cf. Ogden v. Saunders, 12 Wheat. 213, 270; Butler v. Pennsylvania, 10 How.402; Booth v. Illinois, 184 U. S. 425; Henderson Bridge Co. v. Henderson City, 173 U. S. 592, 606, 615; South Carolina Highway Dept. v. Barnwell Bros., 303 U. S. 177, 195.
Interstate Busses Corp. v. Blodgett, 276 U. S. 245; Carley & Hamilton v. Snook, 281 U. S. 66; Continental Baking Co. v. Woodring, 286 U. S. 352; Hicklin v. Coney, 290 U. S. 169; Aero Transit Co. v. Georgia Comm’n, 295 U. S. 285; Morf v. Bingaman, 298 U. S. 407.
If the State had the power to levy the tax, absent congressional proscription, it likewise had the power to extend the grace of exemption to users of its highways of less tank capacity or gasoline load than appellee. Cf. Continental Baking Co. v. Woodring, supra, 370-3; Sproles v. Binford, 286 U. S. 374, 396; Aero Transit Co. v. Georgia Comm’n, supra, 289, 292-3.
303 U. S. 177, 190.
Id., 190.
South Carolina Highway Dept. v. Barnwell Bros., 303 U. S. 177.
Bourjois, Inc. v. Chapman, 301 U. S. 183, 190; Monamotor Oil Co. v. Johnson, 292 U. S. 86, 96; see opinion of Mr. Justice Brandeis, Ashwander v. Tennessee Valley Authority, 297 U. S. 288, 347.
See Mr. Chief Justice Taney, dissenting, Pennsylvania v. Wheeling & Belmont Bridge Co., 13 How. 518, 592.