This case is before this court on a petition of the Commonwealth of Pennsylvania to review the action of the Administrator of the Environmental Protection Agency ('EPA') in promulgating a transportation control plan for Pennsylvania, 40 C.F.R. Part 52, Subpart NN, 38 Fed.Reg. 32884 (November 28, 1971).1 The issues presented are: (1) whether the Administrator erred in including in such plan a regulation requiring the Commonwealth to establish a program to ensure that by June 1, 1976, an air bleed to intake manifold retrofit will be installed on all pre-1968 light-duty motor vehicles in the Pennsylvania portion of the Metropolitan Philadelphia Interstate Air Quality Control Region and the Allegheny County portion of the Southwest Pennsylvania Intrastate Air Quality Control Region, 40 C.F.R. 52.2039, 38 Fed.Reg. 32894 (November 28, 1973); and (2) whether the federal enforcement procedures set forth in 113 of the Clean Air Act (the 'Act'), 42 U.S.C. 1857c-8, may be constitutionally applied to the Commonwealth if it fails to enforce the air bleed retrofit program, or any other provision of the implementation plan promulgated for Pennsylvania, 40 C.F.R. 52.23, 38 Fed.Reg. 30633 (November 6, 1973).

Pursuant to the requirements of 109 of the Act, 42 U.S.C. 1857c-4, the Administrator promulgated, on April 30, 1971, national primary and secondary air quality standards for particular pollutants.2 Under 110 of the Act, 42 U.S.C. 1857c-5, the states were required to submit a control strategy or implementation plan whereby the quantities of these prescribed air pollutants would be reduced to acceptable levels as defined by the primary and secondary standards.

Three of the pollutants for which states had to develop control strategies-- carbon monoxide, hydrocarbons, and photo-chemical oxidants-- are largely attributable to motor vehicles. As a consequence, Pennsylvania, as well as many other states, had to formulate a strategy capable of controlling emissions from mobile sources and could not rely on previous plans designed to control pollution from stationary sources. Because of the general lack of experience in this area, the Administrator, on May 31, 1972, permitted those states who could not rely on a stationary source approach to defer submission of their transportation control strategies for approximately one year beyond the statutory deadline, until February 15, 1973, and granted 21 states, including Pennsylvania, a two-year extension for the attainment date of the standards, until mid-1977, although their plans had not yet been submitted. 37 Fed.Reg. 10842. These actions by the Administrator were held to be beyond his authority under the Act in Natural Resources Defense Council v. Environmental Protection Agency, 154 U.S.App.D.C. 384, 475 F.2d 968 (1973). Thereafter, the Administrator notified the Commonwealth that its extensions were cancelled and that its implementation plan had to be submitted by April 15, 1973, and had to contain a strategy to meet the national ambient standards by mid-1975.

Pennsylvania was one of eight states to submit a control strategy by the April 15, 1973, deadline. On June 15, 1973, the Administrator approved the general strategies proposed by the Commonwealth but disapproved certain provisions of the plan dealing with the methods adopted for implementing the strategies. On July 3, 1973, pursuant to his authority under 110(c)(2) of the Act, 42 U.S.C. 1857c-5(c)(2), the Administrator proposed regulations to bring the Pennsylvania plan into compliance with the Act and to achieve further emission reductions in the Pittsburgh and Philadelphia areas. After public hearings on these proposals were held in Philadelphia and Pittsburgh, a transportation control plan was promulgated on November 28, 1973, for the Metropolitan Philadelphia and Southwest Pennsylvania Air Quality Control Regions, 40 C.F.R. Part 52, Subpart NN, 38 Fed.Reg. 32884.

In addition to the air bleed retrofit program, the Pennsylvania Transportation Control Plan requires the Commonwealth to establish an inspection system for certain motor vehicles to ensure that they do not emit carbon monoxide and hydrocarbons above the level prescribed by EPA, to set up bikeways in the Southwest Pennsylvania and Philadelphia Regions, to establish a computer carpool matching system for those Regions, to create exclusive bus and carpool lanes throughout Metropolitan Philadelphia and Pittsburgh, to limit public parking in the above-mentioned Regions, and to monitor carbon monoxide and hydrocarbon emissions to determine if the measures prescribed by EPA are effective. These parts of the plan were not challenged by the petition for review.

An air bleed to intake manifold retrofit is basically a device designed to introduce excess air into the intake system of a motor vehicle; this results in a more complete burning of the fuel and thus reduces the amounts of hydrocarbons (unburned fuel) and carbon monoxide (burned fuel) emitted into the atmosphere. Under the transportation control plan promulgated by the Administrator, the Commonwealth must establish a program to ensure that all pre-1968 automobiles in the Metropolitan Philadelphia and Allegheny County Regions are equipped with an appropriate air bleed retrofit device. In particular, the Commonwealth is required to submit to the Administrator legally adopted regulations necessary to establish such a program, to cease registering or allowing to operate on its streets and highways vehicles which do not comply with the standards and procedures adopted pursuant to those regulations, and to submit to the Administrator a detailed compliance schedule showing the steps it will take to establish and enforce that program. 40 C.F.R. 52.2039, 38 Fed.Reg. 32894.3

In Delaware Citizens for Clean Air, Inc. v. Administrator, U.S. Environmental Protection Agency, 480 F.2d 972, 976 (3d Cir. 1973), we held that the proper scope of review of the Administrator's approval of state implementation plans under 110 of the Act, is that such action will be set aside only if it is 'arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law' within the meaning of 5 U.S.C. 706(2)(A). Quoting from the Supreme Court's opinion in Citizens To Preserve Overton Park, Inc. v. Volpe, 401 U.S. 402, 416, 71 S. Ct. 814, 823, 28 L. Ed. 2d 136 (1971), we said:

"To make this finding the court must consider whether the decision was based on a consideration of the relevant factors and whether there has been a clear error of judgment. (Citing authorities.) Although this inquiry into the facts is to be searching and careful, the ultimate standard of review is a narrow one. The court is not empowered to substitute its judgment for that of the agency."

Delaware Citizens for Clean Air, supra, 480 F.2d at 976. Although the action challenged by petitioner here is not the approval of a state implementation plan but rather the promulgation of a federal plan to take the place of a rejected state plan, the latter action by the Administrator is also taken pursuant to his authority under 110 of the Act and the same standard of review should apply.

The Commonwealth advances a number of arguments why the action of the Administrator in requiring the establishment of an air bleed retrofit program should be set aside. With regard to the application of that program to the Allegheny County portion of the Southwest Pennsylvania Intrastate Air Quality Region, the Commonwealth points out that in devising a strategy for that area, the Administrator relied on readings taken by the Allegheny County Air Pollution Bureau, which tended to over-estimate the amount of carbon monoxide in the ambient air.4 EPA has conceded this error and has informally advised the Commonwealth that:

'As a result of the deficiencies in the carbon monoxide air quality measurements for Pittsburgh, we have agreed that the data base is inadequate for determining and promulgating appropriate CO-oriented strategies . . .. Our initial judgment is that the CO-oriented air bleed retrofit (required by regulation, Section 52.2039, 38 F.R. 32884) should be reevaluated and possibly substituted by an equivalent HC-oriented device, but that the remaining parts of the promulgation would be essentially the same.'5

As a result, the Administrator does not contest the Commonwealth's argument that a revision of the transportation control plan for the Pittsburgh area may be necessary and has indicated in its brief that a reevaluation process will be initiated shortly.6 However, the Administrator has yet to revoke 52.2039 as it relates to Allegheny County or to announce formally a reconsideration of the carbon monoxide elements of the transportation strategy for that area. Since it is undisputed that there is presently no factual support for the establishment of an air bleed retrofit program in Allegheny County, that part of the Pennsylvania Transportation Control Plan requiring the Commonwealth to do so is arbitrary and capricious and must be set aside.

The Commonwealth sets forth several reasons why the application of the air bleed retrofit program to the Pennsylvania portion of the Metropolitan Philadelphia Interstate Air Quality Control Region should also be set aside. First, it argues that this program is not a 'practicable' method for achieving the primary ambient standard for carbon monoxide in that area, as required of state implementation plans by the Act.7 In particular, the Commonwealth contends (1) that the Administrator incorrectly assumed, without any support from his own engineering data, that an air bleed retrofit device would achieve a 58% Reduction per car in carbon monoxide emissions8 and (2) that the Administrator failed to consider the economic and social impact and cost-effectiveness of an air bleed retrofit program for pre-1968 cars.9 Furthermore, the Commonwealth argues that this matter should be remanded to the Administrator for further proceedings to determine whether an air bleed retrofit program is necessary in light of current petroleum allocation regulations. After a careful review of the record, we have concluded that the above-mentioned arguments of the Commonwealth are without merit and that the Administrator did not act in an arbitrary or capricious manner in requiring the establishment of an air bleed retrofit program to the Metropolitan Philadelphia area.

To begin with, the Administrator's determination that the use of an air bleed retrofit device on pre-1968 automobiles will result in a 58% Reduction per car in carbon monoxide emissions is based on the study 'Control Strategies for In-Use Vehicles.' That study established the 58% Reduction figure as the statistical mean of the reductions obtained from a test series involving 18 low-mileage tests of the air bleed retrofit device conducted upon pre-1968 tuned automobiles.10

(Record Doc. 26, table 3-3 and p. 3-24). We see no reason why the Administrator could not reasonably rely on the results obtained from these tests, since they reflect realistically the actual conditions under which pre-1968 automobiles are used in an urban setting.11

There is also ample evidence in the record to demonstrate that the Administrator gave adequate consideration to the social and economic impact and cost-effectiveness of an air bleed retrofit program. The Administrator recognized from the outset that the costs of such a program would fall heavily on the poor.12

However, its inclusion in the plan promulgated for the Commonwealth is justified by the fact that, according to the technical data available to EPA, the air bleed retrofit program is a practicable and efficient method for reducing carbon monoxide emissions in pre-1968 automobiles.13 In particular, an EPA staff study entitled 'The Clean Air Act and Transportation Controls: An EPA White Paper,' indicates that if the date of implementation is 1977, an air bleed retrofit program for pre-1968 automobiles would be over six times as cost-effective as the next best technique in controlling carbon monoxide emissions on a region-wide basis (Record Doc. 33, p. 16). None of the other reports relied on by the Commonwealth casts any serious doubt on the cost-effectiveness of the air bleed retrofit program.14 Although there is some question as to the exact aggregate reduction in carbon monoxide emissions that would be achieved by such a program, there is sufficient evidence that its contribution to the control of carbon monoxide emissions would be significant.15 In sum, the record makes clear that the Administrator's decision to include the air bleed retrofit program in the control plan for the Metropolitan Philadelphia area 'was based on a consideration of the relevant factors' and we are not persuaded by the arguments and data adduced by the Commonwealth that 'there has been a clear error of judgment.' Citizens To Preserve Overton Park, Inc. v. Volpe, supra, 401 U.S. at 416, 91 S. Ct. at 824 as quoted at page 250 above.

Finally, we do not believe that the current petroleum allocation regulations, 10 C.F.R. 211 et seq., 39 Fed.Reg. 1933 (January 15, 1974), necessitate that the Pennsylvania Transportation Control Plan be remanded to the Administrator for further consideration. It may be, as the Commonwealth contends, that these regulations will substantially reduce carbon monoxide emissions in the Philadelphia area by restricting purchases of fuel and thus decreasing the number of vehicle miles travelled. However, as the Commonwealth acknowledges, 'the length of time the current gasoline shortage will require the enforcement of a wholesale allocation scheme remains a matter of doubt' (brief, p. 25). In fact, the law under which the allocations are made is due to expire on February 28, 1975 (4(g)(1), Emergency Petroleum Allocation Act of 1973, Pub.L. No. 93-159). The Pennsylvania Transportation Control Plan, on the other hand, does not call for achieving the air quality standards in Philadelphia until May 31, 1976. Thus, while the persistence of the gasoline shortage until 1976 might then make the revision of the plan advisable, the situation is too uncertain at this time to justify a remand by this court.

The transportation control plan originally proposed by the Administrator for Pennsylvania, like that proposed for other states, contained provisions regarding violations and enforceability of the substantive regulations contained therein. See proposed 40 C.F.R. 52.2037(g), 52.2038(c), 52.2039(b) (8), 52.2040(e), and 52.2042(f), 38 Fed.Reg. 17797-99 (July 3, 1973). For reasons of administrative convenience, and with no intent to change their meaning or effect, these provisions were deleted from the final regulations promulgated for each state and were replaced by a general regulation on these matters which is applicable to all regulations promulgated by the Administrator as part of the transportation control plan for those states whose own implementation plan has been found inadequate. 38 Fed.Reg. 30633 (November 6, 1973). That regulation, 40 C.F.R. 52.23, reads as follows:

'52.23 Violation and enforcement.

'Failure to comply with any provisions of this part shall render the person or Governmental entity so failing to comply in violation of a requirement of an applicable implementation plan and subject to enforcement action under Section 113 of the Clean Air Act. With regard to compliance schedules, a person or Governmental entity will be considered to have failed to comply with the requirements of this part if it fails to timely submit any required compliance schedule, if the compliance schedule when submitted does not contain each of the elements it is required to contain, or if the person or Governmental entity fails to comply with such schedule.'

Under 113(a) & (b) of the Act,16 the Administrator may at the appropriate time enforce any requirement of an applicable implementation plan by issuing an order to comply or by bringing a civil action against any person in violation of such requirement. In addition, under 113(c) any person who knowingly violates any requirement of an applicable implementation plan or violates or fails or refuses to comply with an order issued by the Administrator is subject to criminal sanctions.

In its petition the Commonwealth challenges the constitutionality of the Administrator's action in making the enforcement procedures of 113 of the Act applicable to the Commonwealth for any failure by it to implement the provisions of the Pennsylvania Transportation Control Plan, arguing that such action exceeds the federal commerce power. The implications of this argument, however, extend far beyond the question of the validity of a single regulation. The power of the Administrator to apply the federal enforcement procedures to the Commonwealth as contemplated in 40 C.F.R. 52.23 depends on the constitutionality of the substantive regulations to be enforced. See Employees of the Department of Public Health and Welfare v. Department of Public Health and Welfare, 411 U.S. 279, 93 S. Ct. 1614, 36 L. Ed. 2d 251 (1973); Maryland v. Wirtz, 392 U.S. 183, 88 S. Ct. 2017, 20 L. Ed. 2d 1020 (1968); Parden v. Terminal Ry. of the Alabama State Docks Department, 377 U.S. 184, 190-192, 84 S. Ct. 1207, 12 L. Ed. 2d 233 (1964). Furthermore, the effectiveness of state implementation of those regulations depends as a practical matter on the availability of federal enforcement for noncompliance by the states. Thus, while the primary focus of the Commonwealth's attack is the threatened use against it of the sanctions authorized by 113 of the Act, the underlying issue is the power of the Federal Government to require a state to enforce an implementation plan. Although in its challenge to the substantive portion of the Pennsylvania Transportation Control Plan, see Part I, supra, the Commonwealth purports to object only to the air bleed retrofit program, the effect of its constitutional argument is to question its obligation to implement any provision of that plan.17

In view of the policy of federal courts to avoid passing upon a constitutional question if a case can be decided on statutory grounds, see Rescue Army v. Municipal Court, 331 U.S. 549, 568-569, 67 S. Ct. 1409, 91 L. Ed. 1666 (1947); Ashwander v. TVA, 297 U.S. 288, 347, 56 S. Ct. 466, 80 L. Ed. 688 (1936) (Brandeis, J., concurring), we shall consider first whether Congress intended, when it passed the Clean Air Amendments of 1970, to require the states to enforce applicable implementation plans and to subject them to federal sanctions if they failed to meet this obligation. After resolving this issue, we shall turn to the constitutional question presented by the Commonwealth.

The language of the Act demonstrates that, in at least some cases, Congress was willing to subject states to implementation plan requirements and to federal enforcement of them. Section 113 provides that enforcement actions may be taken against 'any person,' a term defined in 302(e), 42 U.S.C. 1857h(e), to include any 'State, municipality, and political subdivision of a State.' Section 113 also provides that such action may be taken when there has been a violation of 'any requirement' of an applicable implementation plan. The only question, then, as to the statutory authority for the Administrator's actions in this case is whether Congress contemplated that an implementation plan might require a state to enforce the substantive transportation control provisions of such plan. We have concluded that Congress did contemplate that possibility and that, therefore, the Administrator is authorized to require the Commonwealth to enforce its transportation control plan.

There can be little doubt that Congress intended sweeping changes to be made in transportation and land-use policies where that was necessary to achieve national air quality standards.18 In this case the Administrator has determined that to reduce vehicle emissions and attain such standards, the Philadelphia and Pittsburgh Regions need an inspection and maintenance system, an air bleed retrofit program, bikeways, carpools, busways, and on-street parking restrictions. See page 249, supra. There are only two ways in which the Administrator could ensure that these strategies would be implemented: by applying the resources of the Federal Government to implementing them or by requiring the Commonwealth to do so. For reasons set forth in detail in the general preamble to all the transportation control plans, the Administrator felt that direct federal enforcement was not the means contemplated by the Act. 38 Fed.Reg. 30632-33 (November 6, 1973). Such a determination by the responsible agency is, of course, entitled to 'great deference,' Udall v. Tallman, 380 U.S. 1, 16, 85 S. Ct. 792, 13 L. Ed. 2d 616 (1965), particularly since it represents the judgment of one charged with carrying out the statutory provisions 'while they are yet untried and new,' Norwegian Nitrogen Products Co. v. United States, 288 U.S. 294, 315, 53 S. Ct. 350, 358, 77 L. Ed. 796 (1933).

One of the principal reasons why the Administrator rejected federal implementation of transportation control strategies was that such an approach was inefficient and impractical. It would require the Federal Government to set aside bus lanes and thereby take detailed responsibility for the regulation of roads and highways which, at present, are patrolled and maintained by state agencies. Similarly, it would require the establishment of federally staffed and operated inspection and maintenance and retrofit programs for vehicles which, at present, are registered inspected, and regulated almost exclusively at the state and local level. Thus, the Administrator concluded: 'It is clearly necessary that implementation of transportation control plans be carried out at the State and local level.' 38 Fed.Reg. 30633. It is well established that a court may not 'in the absence of compelling evidence that such was Congress' intention . . . prohibit administrative action imperative for the achievement of an agency's ultimate purposes.' Weinberger v. Bentex Pharmaceuticals, Inc., 412 U.S. 645, 653, 93 S. Ct. 2488, 2494, 37 L. Ed. 2d 235 (1973), quoting Permian Basin Area Rate Cases, 390 U.S. 747, 780, 88 S. Ct. 1344, 20 L. Ed. 2d 312 (1968). The legislative history of the Clean Air Amendments of 1970, far from demonstrating such a prohibition, shows a clear expectation that the states would have to implement significant portions of their transportation control plans and indicates an underlying assumption that they could be required to do so.

Section 110(a)(2)(G) of the Act requires each state implementation plan to provide 'to the extent necessary and practicable, for periodic inspection and testing of motor vehicles to enforce compliance with the applicable emission standards.' Since states are to promulgate such plans, the natural inference to be drawn from this language is that Congress intended for each state to provide for inspection and maintenance of automobiles registered within it. This conclusion is supported by the legislative history of the Act. The House Report on the bill said:

'The legislation provides that States must require inspection of motor vehicles in actual use if the . . . (Administrator), after consultation with the State, determines that the achievement of ambient air quality standards requires such inspection and that such inspection is technologically and economically feasible.'

H.Rep. No. 91-1146, 91et Cong., 2d Sess. 3-4 (June 3, 1970). The Senate Report is to the same effect:

'The implementation plan section of the proposed bill would specifically provide that, to the extent necessary, each region develop motor vehicle inspection and testing programs for which it is eligible to receive assistance under Section 208 (now 210) of the proposed bill. The Committee believes that this is an extremely important provision . . .. It is also a class of air pollution sources for which the regions and the States have better opportunities to control.'

S.Rep. No. 91-1196, 91st Cong., 2d Sess. 13 (September 17, 1970).

In view of Congress' willingness to require states, where necessary, to establish and operate a periodic inspection of all state-registered automobiles, it seems unlikely that it would have had any objection to requiring states to carry out other programs to redece pollution from in-use vehicles. Indeed, the legislative history is replete with indications that Congress contemplated just such an approach. Congressman Staggers, the floor manager of the bill on the House side, put the matter most forcefully:

'If we left it all to the Federal Government, we would have about everybody on the payroll of the United States. We know this is not practical. Therefore, the Federal Government sets the standards, we tell the States what they must do and what standards they must meet. These standards must be put into effect by the communities and the states, and we expect them to have the means to do the actual enforcing.'

116 Cong.Rec. 19204 (June 10, 1970). Almost every other reference to the implementation and enforcement of transportation controls in the legislative history reflects the same view.19 In sum, Congress clearly contemplated that states could be required to implement a transportation control plan, and thus the Administrator's action in promulgating regulations containing such a requirement for the Commonwealth and applying federal enforcement procedures to it was within his statutory authority.

The Commonwealth does not dispute that air pollution has an effect upon commerce and hence can be validly regulated by Congress. United States v. Bishop Processing Co., 287 F. Supp. 624, 630-632 (D.Md.1968), aff'd, 423 F.2d 469 (4th Cir.), cert. denied, 398 U.S. 904, 90 S. Ct. 1695, 26 L. Ed. 2d 63 (1970). See Katzenbach v. McClung, 379 U.S. 294, 303-304, 85 S. Ct. 377, 13 L. Ed. 2d 290 (1964); Heart of Atlanta Motel, Inc. v. United States, 379 U.S. 241, 253-259, 85 S. Ct. 348, 13 L. Ed. 2d 258 (1964). Thus, the Federal Government clearly has the power to direct individual vehicle owners to equip their automobiles with emission control devices and to observe federal traffic and parking controls designed to reduce air pollution.20 Furthermore, it is well established that

'while the commerce power has limits, valid regulations of commerce do not cease to be regulations of commerce because a State is involved. If a State is engaging in economic activities that are validly regulated by the Federal Government when engaged in by private persons, the State too may be forced to conform its activities to federal regulation.'

Maryland v. Wirtz, supra, 392 U.S. at 197, 88 S. Ct. at 2024. See also United States v. California, 297 U.S. 175, 183-185, 56 S. Ct. 421, 80 L. Ed. 567 (1936). The Commonwealth argues, however, that in proposing and enforcing transportation control plans under the Clean Air Act, a state is not engaging in activity also engaged in by private persons, but rather is exercising uniquely governmental functions and thus, by requiring the Commonwealth to implement the programs mandated by the transportation control plan, the Administrator has exceeded the limits of the federal commerce power and has unconstitutionally infringed upon the state's sovereignty.

Our consideration of this argument must begin with an analysis of Maryland v. Wirta, supra, where a similar claim was made and rejected. In that case the Supreme Court decided that Congress' power under the Commerce Clause provides a constitutional basis for extending the Fair Labor Standards Act to state-operated schools and hospitals. Although the Court noted that under the facts of the case, there did not appear to be an interference with 'sovereign state functions,'21 it stated that in any case it is inappropriate to pose the issue in this way, since any exercise by the Federal Government of its delegated powers will necessarily 'interfere' with the power of the states. Ibid. 392 U.S. at 195-196, 88 S. Ct. 2017. Rather, the Court framed the question simply as whether a particular statute is a valid regulation of commerce, and it went on to hold that the fact that the activity in question was carried on by a state, rather than a private person, did not affect the federal commerce power to regulate it.

The Commonwealth argues that this decision is limited to the situation where the state is engaging in activities also engaged in by private enterprises. Similarly, it contends that United States v. California, supra, should be interpreted narrowly, as holding only that a stateowned railroad, operated as a non-profit venture for the purpose of facilitating transportation at a port, was subject, like other railroads, to the Safety appliance Act. However, a careful reading of the opinion in Maryland v. Wirtz, supra, reveals that the Court did not intend that the scope of the federal commerce power over state activities should depend on whether such activities were also carried on by private enterprises, but only that the resolution of this constitutional issue should not depend on whether the party to be regulated is a private person or a state.

The Court began its analysis by reaffirming that the power to regulate commerce is limited to activities that affect interstate or foreign commerce and by cautioning that Congress may not use a relatively trivial impact on commerce as an excuse for broad, general regulation of state or private activities. Maryland v. Wirtz, supra, 392 U.S. at 196-197, and n.27, 88 S. Ct. 2017. It therfore felt that 'the Court has ample power to prevent what the appellants purport to fear, 'the utter destruction of the State as a sovereign political entity." Ibid. at 196, 88 S.Ct. at 2024. The Court then proceeded to quote with approval the following language from United States v. California:

"We think it unimportant to say whether the state conducts its railroad in its 'sovereign' or in its 'private' capacity. That in operating its railroad it is acting within a power reserved to the states cannot be doubted. The only question we need consider is whether the exercise of that power, in whatever capacity, must be in subordination to the power to regulate interstate commerce, which has been granted specifically to the national government. The sovereign power of the states is necessarily diminished to the extent of the grants of power to the federal government in the Constitution.

. . . .nis

"We look to the activities in which the states have traditionally engaged as marking the boundary of the restriction upon the federal taxing power. But there is no such limitation upon the plenary power to regulate commerce. The state can no more deny the power if its exercise has been authorized by Congress than can an individual.' 297 U.S., at 183-185, 56 S.Ct. at 424.'

Ibid. at 197-198, 88 S.Ct. at 2024-2025. Finally, the Court concluded its discussion by stating that 'it will not carve up the Commerce power to protect enterprises indistinguishable in their effect on commerce from private businesses, simply because those enterprises happen to be run by the States for the benefit of their citizens.' Ibid. at 198-199, 88 S.Ct. at 2025.

This reasoning indicates that the basis for the Court's decision in Maryland v. Wirtz, supra, is the principle that the constitutionality of federal regulation of state activities is subject to the same analysis as that of private activities; viz. the determinative factor is simply whether they have an impact on interstate commerce. Following this principle, we believe that the Administrator acted within the federal commerce power in requiring the Commonwealth to enforce its transportation plan. As the Administrator has pointed out, 38 Fed.Reg. 30632:

'Transportation is a necessary service. In our society, the form in which it is provided depends overwhelmingly on the regulatory, taxing, and investment decisions made at all levels of government. By building and maintaining roads and highways, by licensing vehicles and operators, by providing a system of traffic laws, and in many other ways, government has encouraged the browth of automobile use to its present levels. There is nothing inevitable about such a choice. Governments could equally well have chosen to discharge their basic function of maintaining a transportation system in ways that would have discouraged the use of single-passenger automobiles, and encouraged the use of mass transit. But often they have not.

'The production of food, electricity, and other consumer and industrial goods is as necessary in our society as transportation. In each case, the Clean Air Act authorizes regulations requiring such an activity, whether State or private, to be undertaken in the least polluting way in order to attain and maintain the air quality standards. There is no valid distinction between such production facilities and the State-owned automotive transportation facilities. In a comparable situation, the Supreme Court has held that State-owned rail transportation facilities must comply with Federal safety regulations.'

The fact that for historical reasons automotive transportation systems, unlike railways,22 are not operated by private enterprises but only by state and local governments is irrelevant. The states have, by their transportation policies, contributed to the problem of air pollution from automobile emissions, and they can be required to take affirmative actions to correct it, The Commonwealth cannot, by denominating traffic control and vehicle registration as 'governmental' activities, immunize them from federal regulation designed to reduce air pollution.

The Commonwealth contends, nevertheless, that the transportation control plan promulgated by the Administrator unconstitutionally interferes with the performance of its governmental functions because it requires the Commonwealth in effect to enforce a federal regulation. In support of this contention, the Commonwealth cites New York v. United States, 326 U.S. 572, 66 S. Ct. 310, 90 L. Ed. 326 (1946), a case involving the limits upon the federal taxing power. However, we do not believe that the somewhat conflicting principles stated there in the plurality opinions23 are applicable to this case. Since the time of Gibbons v. Ogden, 9 Wheat. 1, 6 L. Ed. 23 (1824), the Supreme Court has recognized that the commerce power is less restricted than the federal taxing power, and it has held that the standards developed to define the boundaries of state immunity from federal taxation are inapplicable to federal regulation of state activities under the Commerce Clause. See United States v. California, supra, 297 U.S. at 185, 56 S. Ct. 421. In New York v. United States, supra, the Court sharply limited that traditional immunity, and in dicta Justice Frankfurter stated that 'the power of Congress to lay taxes has impliedly no less a reach than the power of Congress to regulate commerce.' Ibid. 326 U.S. at 582, 66 S. Ct. at 314. The concern with state sovereignty expressed in that case has never been echoed, however, in subsequent cases involving the commerce power. On the contrary, in Parden v. Terminal Ry. of the Alabama State Docks Department, supra, 377 U.S. at 192, 84 S. Ct. at 1212, the Supreme Court stated:

'By empowering Congress to regulate commerce, then, the States necessarily surrendered any portion of their sovereignty that would stand in the way of such regulation.'

Furthermore, as noted above at p. 259, Maryland v. Wirtz casts doubt on the validity of a challenge to the federal commerce power made in terms of 'interference with sovereign state functions.'

After careful consideration, we do not find that the implomentation plan here under attack conflicts with the proper functioning of the system of federalism embodied in our Constitution. It is true, of course, that such enforcement may be financially burdensome, but that fact is irrelevant, for 'when Congress does act (under the commerce power), it may place new or even enormous fiscal burdens on the States.' Employees of the Department of Public Health and Welfare v. Department of Public Health and Welfare, supra, 377 U.S. at 284, 93 S. Ct. at 1618. It is also true that compliance with the plan will require the Commonwealth to exercise its legislative and administrative powers, for that is the means by which a state regulates its transportation system. However, it must not be forgotten that when dealing with the commerce power, 'we are guided by practical considerations.' Overstreet v. North Shore Corp., 318 U.S. 125, 128, 63 S. Ct. 494, 496, 87 L. Ed. 656 (1943). In enacting the Clean Air Amendments of 1970, Congress created an interlocking governmental structure in which the Federal Government and the states would cooperate to reach the primary goal of the Act-- the attainment of national ambient air quality standards. Under its provisions, state and local governments retain responsibility for the basic design and implementation of air pollution strategies, subject to approval and, if necessary, enforcement by the Administrator. We believe that this approach represents a valid adaption of federalist principles to the need for increased federal involvement. The only alternative implementation would be for the Federal Government to assume some of the functions of traffic control and vehicle registration and directly enforce the programs contained in the various transportation control plans. The Administrator has determined that this would not be a practicable way of attaining taining national air quality standards, see page 257, supra, and we fail to see how this would represent less of an intrusion upon state sovereignty.

We therefore conclude that the application of the federal enforcement procedures to the Commonwealth for noncompliance with the regulations contained in the Pennsylvania Transportation Control Plan is a valid exercise of the federal commerce power. We recognize that there may remain a legitimate concern for possible intrusions upon the proper functioning of our federalist system as a result of future developments in the implementation of the Clean Air Act, and this court will remain ready to protect that concern in any appropriate case. However, as Justice Frankfurter cautioned in New York v. United States, supra, 326 U.S. at 583, 66 S. Ct. at 314.

'The process of Constitutional adjudication does not thrive on conjuring up horrible possibilities that never happen in the real world and devising doctrines sufficiently comprehensive in detail to cover the remotest contingency.'

Thus, the extent to which each of the specific sanctions provided in 113 (see note 16 above) may be imposed on a state or its representatives can more appropriately be determined in a specific case on a definite record.

For the foregoing reasons, that part of 40 C.F.R. 52.2039(b) which makes the air bleed retrofit program applicable to the Allegheny County portion of the Southwest Pennsylvania Air Quality Control Region will be set aside; in all other respects the Petition for Review will be denied, since the remainder of 40 C.F.R. 52.2039 and the federal enforcement procedures set forth in 113 of the Clean Air Act and applied to the Pennsylvania Transportation Control Plan by 40 C.F.R. 52.23 are valid.