Vacated and remanded by published opinion. Senior Judge PHILLIPS wrote the majority opinion, in which Judge NIEMEYER joined. Judge LUTTIG wrote an opinion concurring in the judgment.
OPINION
PHILLIPS, Senior Circuit Judge:The American Trucking Associations, Inc. (“ATA”), the national trade association of the trucking industry, petitions for review of a final rule issued by the Department of Transportation (“DOT”) and the Federal Highway Administration (“FHWA”) that mandates preemployment testing of commercial truck drivers for alcohol use. ATA argues that the rule is based on an erroneous interpretation of the governing statute and is therefore not a reasonable exercise of the agencies’ interpretive discretion. We agree. Accordingly, we vacate the final rule and remand to the *407agencies for further rulemaking consistent with this opinion.
I.
The Omnibus Transportation Employee Testing Act of 1991 (“Act” or “1991 Act”), Pub.L. No. 102-143, Title V, 105 Stat. 952 (1991), directed the Secretary of Transportation to prescribe regulations for the testing of employees for drugs and alcohol in four sectors of the transportation industry. The portion of the Act here at issue directs DOT, “in the interest of commercial motor vehicle safety,” to
establish a program which requires motor carriers to conduct preemployment, reasonable suspicion, random, and postacci-dent testing of the operators of commercial motor vehicles for use, in violation of law or Federal regulation, of alcohol or a controlled substance. The Secretary may also issue regulations, as the Secretary considers appropriate in the interest of safety, for the conduct of periodic recurring testing of such operators for such use in violation of law or Federal regulation.
§ 5(a)(1), 105 Stat. 959 (codified at 49 U.S.C.App. § 2717(a)). Similar provisions apply to air carriers,, railroads, and mass transit authorities as well. § 3(a)(1), 105 Stat. 953; § 4, 105 Stat. 957; § 6(b)(1), 105 Stat. 962.
On December 15, 1992, FHWA and the other operating administrations within DOT1 issued Notices of Proposed Rulemaking (“NPRMs”) to implement the Act’s mandates. DOT itself issued a common preamble which it explicitly incorporated into each of its administrations’ separate NPRMs. 57 Fed.Reg. 59,382 (1992). Because the administrations had previously promulgated drug testing rules,2 the NPRMs and the DOT preamble focused clearly on alcohol testing. Each NPRM proposed that employers would be required to administer pre-employment, reasonable suspicion, post-accident, and random testing for both drugs and alcohol. DOT chose not to require periodic recurring testing.
In its preamble, DOT reiterated views it had expressed three years earlier that pre-employment testing “is one of the least useful types of tests when dealing with alcohol.”3 It observed that, because off-duty alcohol use — in contrast to off-duty use of controlled substances — is generally legal, “[ojften, a test result indicating alcohol use may only indicate bad judgment or bad timing ie.g., one notices an employment advertisement after having beer and a hamburger for lunch, immediately applies, and is tested.)” It also acknowledged that pre-employment testing is especially costly. Nonetheless, DOT tersely observed, “[tjhe Act requires pre-employment testing.” “To make such a test more meaningful,” DOT proposed that “employer[sj would have the option of testing during the hiring process or before (preferably just before) the employee starts performing safety-sensitive functions.” 57 Fed.Reg. 59,398.
DOT and its operating administrations received numerous comments critical of the proposal to require pre-employment alcohol testing.. As DOT later observed, “[a] substantial number of commentators were con*408cerned about the costs of pre-employment tests and considered them silly ‘intelligence’ tests and a waste of time.” 59 Fed.Reg. 7321 (1994). One comment, submitted jointly by Southwest Airlines and several of its employee associations, directly challenged DOT’s assertion that the statute required pre-employment alcohol testing. The comment emphasized that, “under its express terms, the Testing Act requires the [DOT operating administrations] to test for alcohol consumption only when such consumption violates a law or Federal regulation.” It continued:
There is no law or Federal regulation, as far as Southwest is aware, which prohibits persons under the influence of alcohol from appearing at an airline to apply for a safety-sensitive job. This being so, under the express terms of the Testing Act, the FAA would appear to be under no legal mandate to prescribe pre-employment testing rules.
J.A. 114 (Joint Comments of Southwest Airlines et al.). ATA also responded to reiterate the ineffectiveness of pre-employment alcohol testing and to contest DOT’s expressed belief that all of its administrations were required to prescribe pre-employment alcohol testing. For this latter argument, ATA relied not upon language from the 1991 Act, but rather upon FHWA’s pre-existing statutory discretion (unique among DOT’s operating administrations) to “waive, in whole or in part, application of any provision of this chapter or any regulation issued under this chapter with respect to [any] class of persons or class of commercial motor vehicles if the Secretary determines that such waiver is not contrary to the public interest.” 49 U.S.C.App. § 2711. ATA urged FHWA to exercise its discretion to waive the pre-employment testing provisions of the Act as to “drivers [of commercial motor vehicles] subject to the pre-employment alcohol testing.” J.A. 131 (Comments of ATA on Alcohol Use and Testing).
On February 15, 1994, the agencies published a final rule containing both substantive prohibitions on the use of alcohol and testing requirements. The substantive provisions provide, inter alia, that no driver “shall perform safety-sensitive functions [i.e., e.g., waiting to be dispatched, loading, unloading, and driving] within four hours after using alcohol,” 59 Fed.Reg. 7507 (to be codified at 49 C.F.R. § 382.207), and that drivers may not have “any measured alcohol concentration” while on duty. 59 Fed.Reg. 7515 (amending 49 C.F.R. § 392.5(a)(2)). The testing provisions retained the requirements for pre-employment testing, in addition to post-accident, reasonable suspicion, and random testing. In its common preamble, DOT largely repeated the remarks regarding pre-employment testing from its earlier NPRM. After noting the criticisms levelled at the rule, DOT stated simply: “The Act explicitly requires pre-employment testing for covered transportation industry employees, so we do not have the discretion to eliminate it from these programs.” 59 Fed.Reg. 7321. Yet, DOT continued, in order “[t]o make such a test more meaningful,” the final rule would permit employers to administer the “pre-employment” test “any time prior to the first time the employee performs safety-sensitive functions.” Id.4
Finally, FHWA rejected ATA’s request that it waive application of the Act’s pre-employment testing provision to motor carriers:
Even accepting, for the sake of argument, the comment’s presumption that pre-em-ployment testing is inherently useless, the FHWA does not believe it has the authority to waive all drivers from a major provision of the legislation. Eliminating all pre-employment tests would greatly diminish the number of required tests, and would, in effect, rewrite the statute.
59 Fed.Reg. 7487.
ATA filed a timely petition for review under the Hobbs Act, 28 U.S.C. § 2342(5), which provides for direct review in the courts of appeals of final rules issued by the Interstate Commerce Commission, read in conjunction with 49 U.S.CApp. § 1653(c), which specifies like review of orders issued pursuant to functions transferred from the ICC to DOT. We have previously acknowledged *409that exclusive jurisdiction lies in the courts of appeals to review DOT regulations establishing qualifications for motor carrier employees. See Clark v. Skinner, 937 F.2d 123, 126-27 (4th Cir.1991); see also Center for Auto Safety v. Skinner, 936 F.2d 1315 (D.C.Cir.1991) (per curiam); Owner-Operators Indep. Drivers Ass’n v. Skinner, 931 F.2d 582 (9th Cir.1991).
II.
ATA advances two arguments in support of its petition. First, it argues, the agencies erred as a matter of law in construing the Act unambiguously to require them to adopt the regulation that they did. Second, ATA avers, FHWA erred in concluding that it lacked discretion under 49 U.S.C.App. § 2711 to waive the Act’s pre-employment testing requirements as to the motor carrier industry. We agree with ATA’s first contention and therefore vacate FHWA’s final rule insofar as it mandates pre-employment testing for alcohol, and remand to the agencies for further rulemaking. In order to provide greater guidance to the agencies on remand, we also reach ATA’s second contention. We uphold as a reasonable construction of the waiver provision FHWA’s determination that it lacks discretion to waive a statutory provision as to all motor carrier operators.
A.
The standards that govern our review of an agency’s rulemaking are well established. Under Chevron’s familiar two-step analysis, we first ask “whether Congress has directly spoken to the precise question at issue;” if so, we “must give effect to the unambiguously expressed intent of Congress.” If the statute is ambiguous, however, we must defer to the agency’s interpretation if reasonable or permissible. Chevron USA Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837, 842-43, 104 S.Ct. 2778, 2781-82, 81 L.Ed.2d 694 (1984); De Osorio v. United States INS, 10 F.3d 1034, 1037-38 (4th Cir.1993). In this case, there is much disagreement over whether the Act is ambiguous and, if so, wherein the ambiguity lies. Indeed, the agencies themselves have, over time, expressed conflicting views on this question. We conclude that the statute is in fact rife with ambiguity. We vacate the final rule, however, because the interpretation upon which it was based is plainly unreasonable.
The government’s present view is that Congress has not provided clear and coherent guidance regarding the necessity and scope of pre-employment alcohol testing. On one hand, the agencies argue, “the Act plainly does require pre-employment testing for illegal alcohol use.” Respondents’ Brief, at 18. On the other hand, they continue, because “pre-employment use of alcohol is typically not in violation of law or Federal regulation, the statute apparently directs the Secretary to require an impossibility.”. Id. at 19-20. It seems, in other words, that “Congress assumed that it was possible to do a ‘pre-employment’ test for use of alcohol ‘in violation of law or Federal regulation,’ ” id. at 20, and that such an assumption was factually mistaken. If so, the agencies could not adopt any interpretation of the Act that would give full effect to congressional intent. Specifically, the agencies could actualize only one of two mandates: that carriers employ pre-employment testing (along with reasonable suspicion, random, and post-accident testing) for both alcohol and controlled substances; or that carriers test only for that use of alcohol or controlled substances which is “in violation of law or Federal regulation.” The agencies could realize the latter directive by foregoing pre-employment alcohol testing, or they could realize the former by requiring pre-employment testing notwithstanding that any alcohol use the tests revealed would be lawful.
The agencies contend, however, that they avoided the horns of this dilemma by exploiting a patent ambiguity in the term “pre-employment.” Whereas ATA considers “ ‘pre-employment’ ... an unambiguous term, well recognized in the transportation industry and elsewhere, that unambiguously means prior to hiring an applicant for a job,” Petitioner’s Brief, at 21 n. 15, the government insists that “the term ‘employment’ is commonly used in two senses — one referring to the legal relationship (the sense petitioner prefers), and the other referring to the *410actual activity for which someone is hired.” Respondents’ Brief, at 21. In this latter “activity” sense, “the term ‘employment’ refers to ‘the doing of the work,’ plus a reasonable margin to get to and from the place of work.” Id. (quoting California Casualty Indem. Exchange v. Industrial Accident Comm’n, 21 Cal.2d 751, 135 P.2d 158, 161 (1943)). While it is not unlawful to have consumed alcohol prior to applying for a job with a motor carrier, the argument continues, it is unlawful for an employee to “do[ ] the work” (of driving a truck) after having consumed alcohol. Thus, by requiring “pre-employment” testing for alcohol at any time “[pjrior to the first time a driver performs safety-sensitive functions for an employer,” 59 Fed.Reg. 7508, the agencies “chose the only interpretation [that] makes sense out of both statutory phrases: 1) ‘pre-employment’ test, and 2) testing ‘for violation of law or Federal regulation.’ ” Respondents’ Brief, at 22. Because such an interpretation, the government concludes, is eminently reasonable, the final rule must be upheld under Chevron deference.
The most obvious problem with this ingenious argument is that the proffered rationale bears little resemblance to the final rule actually promulgated. As DOT explained in its common preamble, the final rule permits employers to conduct the “pre-employment” test “any time prior to the first time the employee performs safety-sensitive functions,” including even pre-hiring. 59 Fed. Reg. 7321 (emphasis added). By permitting the pre-employment testing to be conducted pre-hiring (at which point any discovered alcohol use would ordinarily be lawful), the rule does not “require[ ] motor carriers to conduct preemployment ... testing of the operators of commercial motor vehicles for use, in violation of law or Federal regulation, of alcohol.” Furthermore, limiting pre-em-ployment testing to “[p]rior to the first time a driver performs safety-sensitive functions,” 59 Fed.Reg. 7508 (emphasis added), is not consistent with the activity sense of the word “employment.” Whereas the “legal relationship” sense of the word refers to a continuous condition, the “activity” sense refers to a discontinuous one. If “employment” means “the doing of the work,” Respondents’ Brief, at 21, then during the course of his legal relationship with his employer, an individual operator is repeatedly employed, then unemployed, and employed again. Pursuant to the activity sense of employment, the final rule should require testing “prior to each time a driver performs safety-sensitive functions.”
The point is not simply that the agencies stumbled when it came to putting into effect their clever interpretation of the Act. Rather, we believe, the rules themselves belie the agencies’ claim that the statutory interpretation they now advance played any part in their actual decisionmaking process. The government points to no evidence in the record which supports the claim that DOT or FHWA ever recognized either of the two ambiguities that drive the government’s present argument.5 Indeed, the agencies’ contemporaneous remarks suggest the contrary. Most telling is DOT’s statement in its preamble to the final rules, that “[t]he Act explicitly requires pre-employment testing for covered transportation industry employees, so we do not have the discretion to eliminate it from these programs.” 59 Fed. Reg. 7321; see also 57 Fed.Reg. 59,398 (preamble to NPRMs). The agencies failed utterly to acknowledge the apparent inconsistency arising from the Act’s equally explicit requirement that the testing only be “for use, in violation of law or Federal regulation.”
*411It is not plausible, moreover, that the agencies had by this time already conceived that "pre-employment" might mean anything other than "pre-hiring." We can reasonably expect that had DOT at that time adopted the unusual "pre-activity" sense of the word it would have said so. DOT's actual explanation that it would permit "pre-employment" testing to be conducted at any time before the first performance of a safety-sensitive function in order to make the rule "more meaningful" indicates instead the agencies' willingness to take some liber~ties with the plain language of the Act for pragmatic ends. In sum, the record reveals that the agencies read the Act as though it unambiguously requires pre-hiring alcohol testing of all applicants without regard for whether a positive test result would indicate use in violation of law. If the final rule is to withstand even Chevron `s deferential judicial review, it is this actual reasoning that must prove reasonable, not the post hoc rationalization devised during litigation. As the Supreme Court stressed in SEC v. Chenery Corp., the "grounds upon which an administrative order must be judged are those upon which the record discloses that its action was based." 318 U.S. 80, 87, 63 S.Ct. 454, 459, 87 L.Ed. 626 (1943).
As the preceding discussion and the agencies' own arguments during the course of this litigation reveal, however, the interpretation of the Act upon which the agencies actually relied at the rule-making stage is not reasonable. First, if as the agencies themselves now contend, the term "pre-employment" is inherently ambiguous, then the statute did not, as they then believed, unambiguously require pre-hiring testing. Second, for reasons that are somewhat complex, even if, as the agencies then thought, the term did mean "pre-hiring," the statute's ultimate directive remains ambiguous.
The government now argues in its briefs that, if "pre-employment" means "pre-hiring," the statutory language is inherently ambiguous (in the sense of being internally inconsistent). That is, because pre-hiring "use of alcohol is typically not in violation of law or Federal regulation, the statute apparently directs the Secretary to require an impossibifity." Respondents' Brief, at 19-20. In fact, though, the conclusion does not follow from the premise. The government's implicit concession that there e~dsts a class of atypical job applicants for whom the use of alcohol at the time of application would be unlawful establishes that the plain language of the Act does not direct the Secretary to require a flat impossibifity. Thus, if "pre-employment" means "pre-hiring," the plain language of the Act appears to require only pre-hiring testing of the few job applicants whose use of alcohol at the time of application might be in violation of law 6-for example, persons under a state minimum drinking age,7 and persons who apply for employment with a motor carrier even while subject to the alcohol-use regulations of their then-current employment.8 This reading of the statute, though linguistically sound, raises problems of its own. Most conspicuously, it is far from clear how such a reading would really advance the Act's stated purpose of promoting "commercial motor vehicle safety." Therefore, even if "pre-employment" could only reasonably mean "pre-hiring," the overall statutory context and legislative history might provide persuasive grounds to conclude that, despite the force of the Act's plain language, Congress did not really intend to require pre-hiring alcohol testing only of the vanishingly small class of potential applicants *412as to whom alcohol use is proscribed by a general law. Cf. Public Citizen v. United States Dept. of Justice, 491 U.S. 440, 452-55, 109 S.Ct. 2558, 2565-67, 105 L.Ed.2d 377 (1989).
For the foregoing reasons, we conclude that the statute is in critical respects ambiguous. Conceivably, it could be construed to require: pre-activity testing of all applicants; pre-hiring testing only of the small subset of applicants as to whom use of alcohol at the time of the test would be “in violation of law or Federal regulation”; pre-hiring testing of all applicants for use of alcohol and controlled substances; or pre-hiring testing of all applicants but only for use of controlled substances.9 Accordingly, the agencies’ actual interpretation—which ignored all the ambiguities that we have identified—is not reasonable. We must, therefore, vacate the final rule.
On remand, the agencies should determine whether, in light of statutory context and purpose, as well as legislative history, “pre-employment” could reasonably mean anything other than “pre-hiring.” If the agencies answer that question in the affirmative and interpret the statute to require pre-activity testing for use of alcohol in violation of law or Federal regulation, they should promulgate a regulation that actualizes that meaning. For reasons already discussed, the existing final rule does not do so.
If (as seems to us more likely) the agencies determine that pre-employment means pre-hiring, they must confront the possibility— apparently not recognized by either the agencies or ATA prior to oral argument— that the Act requires pre-hiring testing of the small universe of applicants as to whom use at the time of the test would be in violation of law or Federal regulation. Whether such a plain language construction of the Act is consistent with congressional intent (and does not lead to an absurd result) we leave for first instance determination by the agencies. We expect that in order to reach a conclusion on this matter the agencies will, among other things, determine just how large the relevant set of applicants would be and consider what consequences should attach to a positive test result.10 If *413the agencies interpret the Act to require pre-hiring testing of persons whose alcohol use at the time of the test would be unlawful, then they must, of course, promulgate an appropriate rule. If the agencies disapprove this interpretation, it would be their task, in the exercise of their reasoned decisionmaking, to privilege one of Congress' apparently inconsistent mandates-that all alcohol testing be conducted only for illegal usage, and that all applicants undergo alcohol testing before being hired-and to promulgate a rule that accords with that interpretation.
B.
As an alternative challenge to the final rule, ATA contends that FKWA erred as a matter of law in concluding that it lacked statutory "authority to waive all drivers from a major provision of the legislation." The Commercial Motor Vehicle Safety Act of 1986 (as amended by the 1991 Omnibus Transportation Employee Testing Act) provides in part:
Notwithstanding any other provision of this chapter the Secretary may waive, in whole or in part, application of any provision of this chapter or any regulation issued under this chapter with respect to [anyl class of persons or class of commer-cml motor vehicles if the Secretary determines that such waiver is not contrary to the public interest and does not diminish the safe operation of commercial motor vehicles.
49 U.S.C.App. § 2711.11 In light of the agen-des' acknowledged skepticism regarding the utility of pre-employment alcohol testing, ATA's comment below urged FHWA to waive the mandate in accord with its statutory discretion. ATA argues in this petition that, even though F}IWA would not have been obligated to exercise its discretion as ATA had requested, the agency erred as a matter of law in construing the waiver provision as not to extend the power upon which ATA would rely. Because we have concluded that the agencies' erroneous iriterpretation of the 1991 Omnibus Act requires that we vacate the final rule, we need not reach ATA's second contention in order to dispose of this petition. We address it nonetheless so as better to inform the agencies' deibera-tions on remand.
ATA's objection to FHWA's protestation that it lacks power to waive motor carriers from the Act's requirement of pre-employment alcohol testing (such as it may be) can be simpiy stated:
The agencies have offered no explanation as to why "any provision" and "any regulation" do not encompass this provision and this regulation. The plain language of the statute provides only two prerequisites to the Secretary's exercise of his waiver authority: his determination that a waiver "is not contrary to the public interest" and his determination that a waiver "does not diminish the safe operation of commercial motor vehicles."
Petitioner's Brief, at 26. But this argument misapprehends the agencies' reasoning, which is that "class" denotes something less than the whole, and "waiver" is distinguished from "repeal." "In short," the government expiains, "waivers are a device for making sure that a general rule is not applied to special situations in which it makes no sense.
*414Waivers are not a device for deciding that a general rule makes no sense at all and should be scrapped altogether.” Respondents’ Brief, at 29. The issue, under this view, is not (as ATA would have it) whether the waiver provision extends to this particular statute. Surely it does. Presumably the Secretary could waive application of the pre-employment alcohol testing rule as to, say, motor carriers under a certain size or drivers over a certain age. The question, rather, is whether the agencies enjoy discretion to waive application of the 1991 Act — or of any other legislation — as to the entire universe of the intended objects of the particular statutory provision.
The agencies’ contention that they do not reflects a highly defensible interpretation of the waiver provision and is entitled to deference. Commonly understood, administrative “waivers” are a mechanism “to seek out the ‘public interest’ in particular, individualized cases.” WAIT Radio v. F.C.C., 418 F.2d 1153, 1157 (D.C.Cir.1969) (emphasis added). They are not a device for repealing a general statutory directive. Accordingly, we uphold the agencies’ determination that 49 U.S.C.App. § 2711 does not authorize them to waive motor carriers from the 1991 Act’s pre-employment alcohol testing requirement, however they may construe that requirement on remand.
III.
Because DOT and FHWA misinterpreted the Omnibus Transportation Employee Testing Act of 1991, we vacate the agencies’ final rule insofar as it requires alcohol testing of all would-be motor carrier operators prior to their first performance of a safety-sensitive function. We remand for the agencies to reinterpret 47 U.S.C.App. § 2717(a) in the light of this opinion and then to promulgate final rules consistent with that reinterpretation.
VACATED AND REMANDED.
. The FHWA has authority over the trucking industry, one of the four segments of the transportation industry directly affected by the Act. The other affected administrations are the Federal Aviation Administration, the Federal Railroad Administration, and the Federal Transit Administration. Another DOT administration, the Research and Special Programs Administration, also issued an NPRM regarding drug and alcohol testing of employees in the pipeline industry, even though the Act did not so require. Rules ultimately issued by administrations other than FHWA, and affecting industries other than commercial trucking, are not at issue in this case.
. For example, in 1988 FHWA issued a final rule requiring motor carriers to conduct five types of tests for use of controlled substances: preem-ployment, periodic, reasonable cause, post-accident, and random. 53 Fed.Reg. 47,134, 47,151 (1988) (codified at 49 C.F.R. §§ 391.81-391.123 (1993)).
.In 1989, DOT issued an advance notice of proposed rulemaking (“ANPRM”) asking for public comment on whether it should extend its drug-testing rules to cover alcohol use. 54 Fed. Reg. 46,326 (1989). In so doing, it expressly questioned the wisdom of pre-employment alcohol testing. 54 Fed.Reg. 46,337. Final action on the ANPRM was forestalled by congressional passage of the 1991 Act.
. FHWA's final pre-employment testing rale provides in relevant part: "Prior to the first time a driver performs safety-sensitive functions for an employer, the driver shall undergo testing for alcohol and controlled substances.” 59 Fed.Reg. 7508 (to be codified at 49 C.F.R. § 382.301(a)).
. To restate: the government’s present argument is that, by discerning ambiguity in the word “pre-employment,” the agency was able to cure the supposed ambiguity in the broader phrase "pre-employment ... testing for use, in violation of law or Federal regulation, of alcohol.” It deserves mention, perhaps, that this argument relies on two different types of ambiguity. Any ambiguity in the word "employment” lies in "the condition of admitting of two or more meanings,” viz., the "legal relationship” and "activity” senses. Only if "pre-employment” is understood to mean "pre-hiring," does the Act become ambiguous in the sense of "maintaining of two or more logically incompatible beliefs or attitudes at the same time," viz., Congress’ interest in both pre-hiring alcohol testing and testing only for the unlawful use of drugs or alcohol. See Webster’s Third New Int’l Dictionary 66 (1981).
. A conclusion that the Act requires pre-employment alcohol testing only of those persons for whom a positive result would indicate use "in violation of law or Federal regulation" does not entail that the Act would prohibit DOT from requiring pre-employnient testing of all job applicants (On grounds, say, of administrative efficiency). We need not decide whether DOT could exercise its broad statutory grants of power, see 49 u.S.C.App. § 2505(a)(3) & 3102(b)(l), to require more comprehensive "pre-employment" alcohol testing than the 1991 Act might mandate.
. Although the usual minimum age to receive a Commercial Driver's License (CDL) is 21, "farm vehicle drivers" of "articulated motor vehicles" may receive CDLs at 18 if state law permits. See 49 C.F.R. § 391.67(a) (qualifying 49 C.F.R. § 391.11(b)(1)).
. See, e.g., 49 C.F.R. § 219.101(a) (read in conjunction with 45 U.S.C. § 61(b)(3)) (prohibiting alcohol use by railroad employees even during interim rest periods.)
. Judge Luttig, concurring, differs on the critical question whether on this very point the Act is patently ambiguous. He says, post at 414, 417, that it is not. But he also says, presumably by way of demonstrating its unambiguity, that "by its plain terms the Act requires alcohol testing, either before hiring or before work actually begins, for use in violation of law.” Post at 414 (emphasis added). If this does not fit the dictionary (and commonly understood) meaning of patent ambiguity—"the condition of admitting of two or more meanings,” see supra, at 410, n. 5— we are hard put to see why not. There may be a misapprehension of the proper connotation of "plain” in matters of statutory interpretation at work here. The fact that a statute "plainly” directs diametrically conflicting courses of action does not allow a “plain meaning” judicial application of its direction; instead, it creates a patent ambiguity of text that requires—and permits— judicial interpretation of that text by resort to extrinsic sources.
Similarly, we disagree, as a matter of simple logic, with Judge Luttig’s implication, see post at 407, that because the Act also directs reasonable suspicion and random testing, the Government's "pre-activity” reading of "pre-employment” is not a plausible one because it would be redundant. This depends on the assumption that random and reasonable suspicion testing could only be done "pre-activity." But of course they could be done as well during or after the "activity” of driving, the Act does not speak unambiguously on this matter any more than it does on what “pre-employment" means.
. The statute omits any article before the word "class," but was apparently modeled on the Motor Carrier Safety Act of 1984, which authorizes waivers of safety regulations as to "any person or class of persons." 49 U.S.C.App. § 2505W (emphasis added). The parties agree that the article omission was inadvertent and that the provision should be read as written in text.
. Judge Luttig’s concurring opinion identifies a number of statutes and regulations that he believes define classes of applicants whose use of alcohol at the time of pre-hiring testing would be “in violation of law or Federal regulation.” See post at 415-16 & n. 4. We do not think that the literal texts of all of Judge Luttig’s examples support his argument. Nor, however, do we think it necessary or particularly useful to engage in an extended debate at this point over which of his examples are sound and which are not. On remand, the agencies should seek to identify the set of “laws or Federal regulations” that could conceivably be violated by an applicant for a covered job at the time of pre-hiring alcohol testing, and to determine roughly how many persons might he affected.
Of course, such an inquiry would be unnecessary if, as Judge Luttig apparently believes, the Act unambiguously requires pre-hiring testing of all applicants for illegal alcohol use so long as there theoretically exists a single individual whose use of alcohol at the time of pre-hiring testing could be in violation of law or Federal regulation. Were that the unambiguous meaning of the naked text of this passage of the Act— which the ambiguity in the term “pre-employment” makes it impossible to accept—we are *413satisfied that the agencies might properly consider avoiding its application by resort to the "absurd result" canon of statutory interpretation. See, e.g., Public Citizen, 491 U.S. at 455, 109 S.Ct. at 2567 ("Looking beyond the naked text for guidance is perfectly proper when the result it apparently decrees is difficult to fathom or when it seems inconsistent with Congress' intention .); id. at 470, 109 S.Ct. at 2575 (Kennedy, J., concurring); Green v. Bock Laundry Machine Co., 490 U.S. 504, 527, 109 S.Ct. 1981, 1994, 104 L.Ed.2d 557 (1989) (Scalia, J., concurring); Watt v. Alaska, 451 U.S. 259, 266, 101 S.Ct. 1673, 1678, 68 L.Ed.2d 80 (1981) ("The circumstances of the enactment of particular legislation may persuade a court that Congress did not intend words of common meaning to have their literal effect."). Accordingly, a remand for reconsideration of the regulation under the statutory interpretation favored by Judge Luttig would necessarily permit the same general range of inquiry into likely congressional intent that is opened by our interpretation.