concurring:
The Chief Justice, Mr. Justice Roberts, Mr. Justice Reed, and I agree with Mr. Justice McReynolds, but we think a word should be said of appellant’s contention *181that the tax in- its practical operation may be taken as a fair measure of respondent’s use of the highways.
Since the subject taxed, gasoline introduced into the state in the tank of a vehicle, for use solely in propelling it in interstate commerce, is immune from state taxation except for a limited state purpose, the exaction of a reasonable charge for the use of its highways, it is not enough tnat the tax when collected is expended upon the state’s highways. It must appear on the face of the statute or be demonstrable that the tax as laid is measured by or has some fair relationship to the use of the highways for which the charge is made. Sprout v. City of South Bend, 277 U. S. 163, 170; Interstate Transit, Inc. v. Lindsey, 283 U. S. 183, 186; Bingaman v. Golden Eagle Western Lines, 297 U. S. 626, 628; Morf v. Bingaman, 298 U. S. 407; Ingels v. Morf, 300 U. S. 290, 294.
While the present tax, laid on gasoline in the tank in excess of twenty gallons, admittedly has no necessary or apparent relationship to any use of the highways intrastate, appellant argues that, as applied to the reserve gasoline in each of appellee’s vehicles, the tax either is, or with a reduction of the reserves would be, substantially equivalent to a tax which the state could lay, but has not, on the gasoline consumed within the state. That could be true only in case the taxed gasoline, said to be reserved for the extrastate journey, were by chance or design of substantially the same amount as that. consumed intrastate.
That the relationship between tax and highway use does not in fact exist as the business is now conducted, is demonstrated by appellant’s showing that on all of appel-lee’s routes, taken together, the taxed gasoline which is reserved for extrastate use is substantially more than that consumed on those routes within the state. In three the taxed reserve in excess of the twenty gallons exemption is substantially the' same as the amount of the intra*182state consumption. But on the fourth route the taxed reserve on busses moving in one direction is more than four times that consumed within the state. In the other it is approximately the same. With the three scheduled trips daily each way on the Memphis-St. Louis route, the excess of the gasoline taxed over that consumed in the state is more than 150 gallons per day. In no case does it appear that the amount of taxed gasoline has any relation to the size or weight of vehicles.
It cannot be said that such a tax whose equivalence to a fair charge for the use of the highways, when not fortuitous, is attained only by appellee’s abandonment of some of the commerce which is taxed, has any such fair relationship to the use of the highways by appellee as would serve to relieve the state from the constitutional prohibition against the taxation of property moving in interstate commerce. A tax so variable in its revenue production when compared with the taxpayer’s intrastate movement cannot be thought to be “levied only as compensation for the use of the highways.” Interstate Transit, Inc. v. Lindsey, supra, 186. Justification of the tax, as a compensation measure, by treating it as the equivalent of one which could be laid on gasoline consumed within the state must fail because the statute on its face and in its application discriminates against the commerce by measuring the tax by the consumption of gasoline moving and used in interstate commerce which occurs outside the state. See Fargo v. Michigan, 121 U. S. 230, 241; Gwin, White & Prince v. Henneford, 305 U. S. 434, 438.
It is no answer to the challenge to the levy to say that by altering the amount of the gasoline brought into the state for extrastate consumption appellee could so moderate the tax that it would bear a fair relation to the use of the highways within the state. In the circumstances of this case the state is without power to regulate the amount *183of gasoline carried interstate in appellee’s tanks; It cannot be said, if that were material, that the amount carried is not appropriate for the interstate commerce in which appellee is engaged and it can hardly be supposed that the state could compel appellee to purchase there all the gasoline which it uses intrastate upon an interstate journey, because that would be a convenient means of laying and collecting a tax for the use of the highways. There are ways enough in which the state can take its lawful toll without any suppression of the commerce which it taxes. In laying an exaction as a means of collecting compensation for the use of its highways the state must tax the commerce as it is done, and not as it might be done if the state could control it. Appellant cannot justify an unlawful exaction by insisting that it would be lawful if the taxpayer were to relinquish some of the commerce which the Constitution’ protects from state interference.