CORDY, J.

The Massachusetts Bay Transportation Authority (MBTA) appeals from a judgment of the Superior Court affirming a determination of the Massachusetts Commission Against Discrimination (MCAD) that the MBTA discriminated against a prospective employee, David Marquez, in violation of G.L. c. 151B, § 4 (1A). More specifically, the MCAD determined that the MBTA failed reasonably to accommodate Marquez's religious obligations when it refused to hire him as a part-time bus driver due to his need for time off to observe his Sabbath (Friday at sundown until Saturday at sundown). The principal basis for its determination was the failure of the MBTA to meet its statutory burden either to provide a reasonable accommodation for Marquez's sincerely held religious beliefs or to demonstrate that any accommodation that the MBTA could have made would have posed an "undue hardship" on its operations. This failure of proof, in turn, the MCAD concluded, was largely the product of the MBTA's failure to take any steps whatsoever to ascertain whether an accommodation was possible at the time, and evidence from MBTA employees suggesting the existence of a number of possibilities that went unexplored. We transferred the case to this court on our own motion.

In its appeal, the MBTA presents three grounds on which it claims that the MCAD decision should be reversed: (1) requiring the MBTA to give Marquez Friday evenings off would have posed an undue hardship pursuant to G.L. c. 151B, § 4 (1A), or, alternatively would violate the establishment clause of the First Amendment to the United States Constitution, ; (2) requiring the MBTA to engage Marquez in an interactive process for the purpose of identifying possible accommodation would likewise pose an undue hardship on the MBTA; and (3) the relief granted by the MCAD exceeded its authority. We affirm the Superior Court judgment, but not on all the grounds relied on by the judge.

1. Facts. The following material facts are not in dispute. Marquez is a practicing Seventh-Day Adventist, who serves as a deacon of his church in Cambridge. Consistent with the tenets of his religion, Marquez does not work on the Sabbath, which extends from sundown each Friday night to sundown each Saturday night. According to Marquez's beliefs, he could be in transit home after sunset on Friday. He could not, however, work after sunset. He spends each Friday evening at home with his family, sharing Sabbath dinner, and spends each Saturday at his church. Former employers accommodated his religious obligations by allowing him to work on Sunday.

In April, 1997, Marquez applied for a job with the MBTA. Throughout the application process, Marquez informed MBTA representatives that he was not able to work from sundown on Friday to sundown on Saturday. In May, Marquez passed a written examination to become a part-time streetcar operator, and on June 12, 1997, he was given a conditional offer of employment. That offer was contingent on the outcome of a criminal records check, a physical examination, and a drug screening test.

On August 7, 1997, while his background checks were ongoing, Marquez expressed an interest in applying for the position of part-time bus operator. The manager of human resources for the MBTA informed Marquez that he would need a commercial driver's license in order to become a bus operator. Shortly thereafter, Marquez obtained his commercial driver's license. By late August, 1997, he had passed the preliminary screening, testing, and interview process. His physical examination, drug screening, and criminal records check all were unproblematic, and he was cleared for hiring.

Marquez received his assignment to begin bus driver training on September 2, 1997. The training was scheduled to run from Tuesday through Saturday, which conflicted with Marquez's observation of the Sabbath. Marquez notified an MBTA human resources representative of the conflict, who told him that she would "look into the issue."

Other than that one Saturday of training, working on Saturdays did not present any problem, as part-time bus operators work Monday through Friday, for a morning rush hour shift and then an evening rush hour shift each day. Friday evenings, then, became the point of conflict between Marquez's Sabbath obligations and the requirements of his job.

In early September, 1997, the MBTA notified Marquez that it could not grant his request to refrain from working on Friday evenings because of his religious beliefs and, therefore, would not extend an offer of employment. The parties agree that but for Marquez's scheduling needs, he was qualified for the position of part-time bus operator. It is also undisputed that the MBTA never discussed with Marquez any possible accommodation.

In the wake of the MBTA's decision, Marquez suffered significant emotional distress. He felt that he was put in a position where he had to choose between his religion and his ability to work, and his choice made him question his faith. He took a hiatus from serving as a deacon in his church because he felt that he was an inadequate advocate for his religion. Marquez's relationship with his wife began to deteriorate, and he began to drink and smoke cigarettes, in violation of his religious obligations. Only after a period of one and one-half years was he able fully to reembrace his religion.

2. Procedural history. On September 9, 1997, Marquez filed a charge of discrimination against the MBTA with the MCAD. He alleged that the MBTA discriminated against him on the basis of his religion by refusing to accommodate his religious observance of the Sabbath, in violation of G.L. c. 151B, § 4 (1A). The MCAD found probable cause to credit Marquez's allegations and certified the case for a public hearing.

A commissioner conducted a hearing on August 1 and 2, 2001. There was testimony from the manager of the human resources department at the MBTA that in 1997 the MBTA did not have a written policy regarding religious accommodation, but that the standard operating procedure was to ask for documentation supporting the request (which Marquez had provided), and to consult the legal department, the hiring department, the equal employment opportunity department, and the human resources department of the MBTA about potential accommodations. This process of consultation would include weighing factors such as the position the applicant was seeking and the impact any accommodation would have on operational needs, all of which would yield "some tangible evidence or documentation to support [the MBTA's] decision." There was, however, no evidence of any kind, written or oral, offered by the MBTA to establish that it engaged in such a process in response to the request made by Marquez.

The MBTA's chief transportation officer of bus operations testified at the MCAD hearing regarding the MBTA's methods of covering for its many scheduled and unexpected employee absences. When there are insufficient drivers, he testified, the MBTA will use its "cover" list to fill in with relief drivers for any absent ones. If possible, the MBTA will also facilitate voluntary swaps among drivers to limit preventable absences. Although there was at the time a policy forbidding full-time drivers from swapping with part-time drivers, it was a "loose[ly]" enforced policy, and approximately thirty full-time drivers (who would have worked out of the same garage as Marquez) worked on Sundays and not on Fridays, and would have been in a position to swap shifts with Marquez if they chose to do so. There was also testimony that, if necessary, the MBTA would pay other operators overtime to cover for an unmanned route, or even leave the vacant shift uncovered. There was no evidence that any of these methods for covering employee absences was considered by the MBTA in response to Marquez's request for accommodation.

After the hearing, the commissioner issued a written decision, including detailed findings of fact and conclusions of law. The commissioner found that there were a number of possible means by which Marquez's religious beliefs could have been accommodated, including coverage by relief drivers (over which management retained a measure of discretion), or through the use of overtime workers, or by leaving the Friday evening shift uncovered, or by allowing voluntary swaps between part-time and full-time drivers. Notwithstanding these possible accommodations, the MBTA offered no evidence to show that it explored any of them, but had concluded, without investigation, that an accommodation of Marquez's beliefs was not feasible. Consequently, the hearing commissioner found, the MBTA had "refused to even attempt a good faith effort to accommodate [Marquez]" and did not meet its burden of proving undue hardship pursuant to G.L. c. 151B, § 4 (1A). The commissioner awarded Marquez $50,000 for emotional distress and ordered the MBTA to hire Marquez for the position for which he was qualified in 1997, if Marquez still desired to pursue it.

The MBTA appealed from the commissioner's decision to the full commission. The MBTA did not contest that Marquez was qualified to be a part-time bus operator or the commissioner's finding that, despite a loose policy to the contrary, voluntary swaps between part-time bus operators and full-time operators happened frequently. Instead, the MBTA claimed that any accommodation that would have allowed Marquez to leave his bus route early every Friday evening would have caused undue hardship. Therefore, the MBTA contended, it did not need to engage Marquez in an interactive process to ascertain his religious obligations more fully and whether they could be reasonably accommodated. Indeed, the MBTA asserted that requiring such a process would itself be an undue hardship.

The full commission affirmed the commissioner's findings and order of relief, similarly concluding that the MBTA had not sufficiently demonstrated that accommodating Marquez's religious beliefs would cause it an undue hardship. The MCAD also went further, interpreting the reasonable accommodation language of G.L. c. 151B, § 4 (1A), to require that an employer engage in an interactive process with its employee once the employer is notified of an employee's conflicting religious obligation, and concluding that the MBTA's failure to engage in such a process with Marquez was itself a separate violation of the statute. As the MCAD found, "the reasonable accommodation language . . . give[s] rise to a concomitant obligation on the part of an employer to engage in a meaningful dialogue with an employee in order to investigate fully whether a particular accommodation can be made." The MCAD affirmed the relief granted by the commissioner and awarded $53,550 in attorney's fees to Marquez.

Pursuant to G.L. c. 30A, § 14, the MBTA appealed from the MCAD's decision to the Superior Court. A Superior Court judge affirmed the decision of the MCAD, concluding that the MBTA had failed to demonstrate that the possibility of reasonably accommodating Marquez was foreclosed. Modes of accommodation, the judge observed, such as voluntary swaps and the use of relief drivers, may have been available to accommodate Marquez, and the MBTA failed to show that those options would have constituted an undue hardship. The judge noted that no MBTA official consulted with union officials regarding any possible accommodations (shift selections and swaps), and no employees were consulted regarding their willingness to swap shifts with Marquez. Additionally, the judge found that the payment of overtime to an employee to cover Marquez's Friday evening shift would not impose an undue hardship on the MBTA, but that requiring the MBTA to leave a shift uncovered as an accommodation to Marquez's schedule would impose such a hardship. The judge found ample evidence to support the MCAD's finding that the MBTA should have conducted an interactive individualized inquiry seeking to accommodate Marquez, and that such an inquiry is required unless a reasonable accommodation clearly is impossible, which was not the case here. Last, the judge found that the relief ordered by the MCAD, including the award of attorney's fees, was within the commission's discretion.

3. Discussion. We will affirm a decision and order of the MCAD unless its findings and conclusions are unsupported by substantial evidence or are based on error of law. See G.L. c. 151B, § 6; G.L. c. 30A, § 14 (7); School Comm. of Brockton v. Massachusetts Comm'n Against Discrimination, 423 Mass. 7, 11 (1996); New York Mass. Motor Serv., Inc. v. Massachusetts Comm'n Against Discrimination, 401 Mass. 566, 572 (1988).

We begin by noting that the commissioner's findings (adopted by MCAD) that Marquez established a prima facie case of religious discrimination in violation of G.L. c. 151B, § 4 (1A), and that the MBTA failed to take any steps to accommodate him or even to investigate whether any of a number of potential accommodations was possible without incurring undue hardship, are amply supported in the record.

We now turn to the MBTA's two central assertions of error. First, the MBTA asserts that the MCAD's conclusion that it failed to prove that any possible accommodation would have been undue hardship was incorrect as a matter of law. Second, the MBTA asserts that any accommodation of Marquez would have imposed more than a de minimis cost on it in violation of the establishment clause.

In applying G.L. c. 151B, § 4 (1A), the MCAD and the Superior Court judge properly looked to the familiar three-part inquiry that is applied when religious discrimination is alleged. New York Mass. Motor Serv., Inc. v. Massachusetts Comm'n Against Discrimination, supra at 575-576. Initially, the employee bears the burden of proving that the employer required him to violate a religious practice compelled by his sincerely held belief. Id. See Cloutier v. Costco Wholesale Corp., 390 F.3d 126, 137 (1st Cir. 2004), cert. denied, 545 U.S. 1131 (2005) (applying same analysis in context of amended statute). The employee must also demonstrate that he provided his employer with the required advance notice of his religious obligation (ten days). G.L. c. 151B, § 4 (1A). Once the employee establishes these prerequisites, the burden shifts to the employer either to accommodate the complainant or "to prove that accommodation of the complainant's religious obligations would impose on the employer an undue hardship as defined by the statute." New York Mass. Motor Serv., Inc. v. Massachusetts Comm'n Against Discrimination, supra at 576. In determining whether this burden has been met, the MCAD must focus on the particular nature and operations of the employer's business. Id. Additionally, the MCAD must inquire "whether the employer could have exercised its managerial discretion in such a way that the employee's religious obligations could have been reasonably accommodated." Id.

The burden here, then, is on the MBTA to demonstrate that any possible accommodation of Marquez's religious beliefs would have constituted an undue hardship in the context of its operations. An employer's mere contention that it could not reasonably accommodate an employee is insufficient, G.L. c. 151B, § 4 (1A); New York Mass. Motor Serv., Inc. v. Massachusetts Comm'n Against Discrimination, supra, as is its mere speculation. See Brown v. General Motors Corp., 601 F.2d 956, 960 (8th Cir. 1979) (under parallel protections of Title VII of Civil Rights Act of 1964, "employer stands on weak ground when advancing hypothetical hardships in a factual vacuum").

The statute offers four express examples of undue hardship. G.L. c. 151B, § 4 (1A). The term includes the "inability of an employer to provide services which are required by . . . federal and state laws." If the employee's absence would "unduly compromise" public health or safety, then accommodation is unreasonable. Similarly, an employer is not required to accommodate the absence of an irreplaceable employee "where [that] employee's presence is indispensable to the orderly transaction of business." Last, if the employee's presence is "needed to alleviate an emergency situation," his absence will be considered undue hardship. The list of examples is not exhaustive. Cloutier v. Costco Wholesale Corp., supra at 138. Rather, it illustrates the types of accommodation that constitute excessive interference with an employer's business affairs under the statute. Id.

The term "undue hardship" is the same term used in Title VII of the Civil Rights Act of 1964 regarding Federal protections from religious discrimination. 42 U.S.C. §§ 2000e(j), 2000e-2(a)(1) (2006). The United States Supreme Court has interpreted the inclusion of the "undue hardship" provision in Title VII to mean that an employer may not be required to bear more than a de minimis cost to accommodate the religious beliefs of an employee. Trans World Airlines, Inc. v. Hardison, 432 U.S. 63, 84 (1977). Although the Massachusetts undue hardship standard in G.L. c. 151B is "notably different" and allows for slightly broader religious protection, the two share substantial common ground. Pielech v. Massasoit Greyhound, Inc., 441 Mass. 188, 196 (2004) (comparing scope of Title VII and G.L. c. 151B, § 4 [1A]). In that vein, we consider Federal case law construing Title VII in interpreting G.L. c. 151B, § 4 (1A). See, e.g., Wheatley v. American Tel. Tel. Co., 418 Mass. 394, 397 (1994) ("It is our practice to apply Federal case law construing the Federal anti-discrimination statutes in interpreting G.L. c. 151B").

With State and Federal precedents in mind, we agree with the Superior Court judge that the MBTA cannot be forced to accommodate Marquez by leaving his shift uncovered. That decision must be left to the MBTA, and the statute does not require otherwise. G.L. c. 151B, § 4 (1A) ("Undue hardship, as used herein, shall include . . . where the employee's presence is indispensable to the orderly transaction of business and his or her work cannot be performed by another employee of substantially similar qualifications during the period of absence"). We also agree with the MBTA that it need not accommodate Marquez by paying a replacement operator overtime to cover his shift each week, see Trans World Airlines, Inc. v. Hardison, supra at 84 (Title VII does not require employer to pay premium wages to cover for absent employee because that accommodation is unreasonable and constitutes undue burden), and that G.L. c. 151B, § 4 (1A), cannot be read to require employees to swap shifts involuntarily. See id. (Title VII does not so require). However, at the MCAD hearing, the MBTA failed to demonstrate that these were the only methods of accommodation available. We therefore turn to the question of voluntary shift swaps as a means of accommodation.

The MBTA now asserts that its voluntary swap policy could not have guaranteed Marquez a weekly accommodation, ultimately because that policy prevented part-time operators from swapping shifts with full-time operators. Yet, the evidence was that this policy was not official, and that such swaps were frequently allowed. As this court held in New York Mass. Motor Serv., Inc. v. Massachusetts Comm'n Against Discrimination, supra at 578, an employer cannot meet its burden pursuant to G.L. c. 151B, § 4 (1A), by casting a selectively enforced swap policy as a roadblock to accommodation. In that case, the employer purported to enforce a one-man-off vacation policy, but the evidence was that the policy was applied selectively. Id. at 571-572. When the employee requested time off to observe his holy days, the employer contended that such an accommodation was not possible, because of its seniority system and its one-man-off vacation policy. Id. at 578. This court concluded that because that policy was selectively enforced, the employer could have exercised its managerial discretion with de minimis cost and effort to accommodate the complainant. Id. at 578. Similarly, here the swap policy was "loose" and subject to frequent exception, and the MBTA failed to demonstrate that it could not have exercised its managerial discretion to allow Marquez to swap with full-time drivers without incurring more than de minimis cost. Moreover, where the MBTA failed even to explore this possible accommodation, its claim of undue hardship rests, unpersuasively, in a factual vacuum.

In the absence of evidence demonstrating a contractual bar to voluntary employee swaps, or other interference with employer operations, requiring an employer to facilitate such swaps as a means of accommodating the religious observances of its employees will not be considered undue hardship. General Laws c. 151B, § 4 (1A), clearly contemplates that employers will help employees shuffle shifts to allow observance of their Sabbath. Indeed, the only specific religious observance mentioned by the statute is the observance of the Sabbath, G.L. c. 151B, § 4 (1A), and voluntary shifts swaps are one of the most straightforward, and least costly, ways to ensure compliance with the statute's requirements. See Beadle v. Hillsborough County Sheriff's Dep't, 29 F.3d 589, 593 (11th Cir. 1994), cert. denied, 514 U.S. 1128 (1995) (employer reasonably accommodated employee under Title VII by providing him with employee roster sheet that included all coworkers' schedules, and allowing him to advertise his need for shift swaps during daily roll calls and on department bulletin board). While it is possible, as the MBTA contends, that voluntary swap arrangements covering Marquez's shift every Friday evening were unlikely, had the MBTA actually investigated the possibility, its assertions would carry substantially more weight. Brown v. General Motors Corp., 601 F.2d 956, 961 (8th Cir. 1979). The MBTA's blanket assertion that Marquez's demand for relief from the Friday evening shift were unreasonable is an insufficient substitute for that investigation. The MBTA failed to prove that the use of voluntary swaps to accommodate Marquez would impose an undue burden on its operations.

Because the MBTA failed to present evidence that it took any steps to accommodate, or even to investigate possible accommodations for Marquez, we need not address its claim that requiring an employer to incur more than de minimis cost to accommodate an employee violates the establishment clause. See New York Mass. Motor Serv., Inc. v. Massachusetts Comm'n Against Discrimination, supra at 577-579 (when employer has not demonstrated de minimis cost, this court need not consider whether imposition of more significant cost would violate establishment clause).

Finally, the MBTA contends that requiring either an investigative or interactive process in this case would itself be an undue hardship. Such a reading of G.L. c. 151B, § 4 (1A), would eviscerate religious protection in the workplace. If merely looking into an accommodation, or consulting with an employee about his requested accommodation, were to be considered too great an interference with an employer's business conduct, then employers would effectively be relieved of all obligation under G.L. c. 151B, § 4 (1A). General Laws c. 151B, § 9, mandates that "[t]his chapter shall be construed liberally for the accomplishment of its purposes. . . ." To read the statute as the MBTA urges would eviscerate this statutory objective.

We do not agree with the MCAD, however, that an employer's failure to engage in the interactive process is, in and of itself, a violation of G.L. c. 151B, § 4 (1A), irrespective of whether a reasonable accommodation is possible. Although the MCAD generally has the primary responsibility to determine the scope of G.L. c. 151B, § 4 (1A), we note that the plain language of the statute requires only "reasonable accommodation." G.L. c. 151B, § 4 (1A). See Stonehill College v. Massachusetts Comm'n Against Discrimination, 441 Mass. 549, 563, 576 (2004) (noting court's general deference to MCAD in determining scope of G.L. c. 151B, but also holding that commission's presumption of emotional distress damages in retaliation firings was improper). If an employer can demonstrate, for example, that a certain accommodation imposes an undue hardship, it would not be reasonable to require an interactive process each time that accommodation is sought.

We therefore do not require an interactive process without exception. There is no obligation to undertake an interactive process if an employer can conclusively demonstrate that all conceivable accommodations would impose an undue hardship on the course of its business. See Weber v. Roadway Express, Inc., 199 F.3d 270, 275 (5th Cir. 2000); EEOC v. Townley Eng'g Mfg. Co., 859 F.2d 610, 615 (9th Cir. 1988), cert. denied, 489 U.S. 1077 (1989) (employer is not required to engage in fruitless dialogue if it is absolutely clear no accommodation could be made without undue hardship). Such a demonstration, however, will often be difficult to make without the employer's having engaged in an interactive process with the employee and having made a good faith effort to explore the options that come out of such a process. The MBTA has amply demonstrated this point in the case before us.

For this reason, we have encouraged an interactive process in other settings under G.L. c. 151B, even where we have declined to interpret a specific provision to make it mandatory. For example, in the housing context (where landlords are required to make reasonable accommodations for handicapped tenants), we have not required landlords to engage in an interactive process in order to determine what a reasonable accommodation might be, Andover Hous. Auth. v. Shkolnik, 443 Mass. 300, 308 (2005), but have encouraged landlords to do so because "such a process is the optimal way for a landlord and tenant to explore the scope of the tenant's alleged handicap as well as the availability and feasibility of various accommodations." Id. at 308-309. That process is also the optimal way for an employer to meet its burden reasonably to accommodate the sincerely held beliefs of an employee or, alternatively, to show that the employee cannot be accommodated without undue hardship.

4. Relief. The MBTA contends that the MCAD exceeded its discretion by ordering the MBTA to hire Marquez to the position for which he was qualified in 1997, and was required to limit its relief in this regard to requiring the MBTA to investigate whether an accommodation at the present time was possible without imposing an undue burden on its operations. We disagree.

When the MCAD finds an unlawful practice, it may "take such affirmative action, including but not limited to, hiring, reinstatement or upgrading of employees . . . as, in the judgment of the [MCAD], will effectuate the purposes of [G.L. c. 151B]" (emphasis added). G.L. c. 151B, § 5. See New York Mass. Motor Serv., Inc. v. Massachusetts Comm'n Against Discrimination, supra at 581-582 n. 14 (formulation of damage awards under G.L. c. 151B, § 5, is within MCAD's discretion). Cf. Stonehill College v. Massachusetts Comm'n Against Discrimination, supra at 570-576 (discussing MCAD's broad remedial powers, but holding that when those powers are used to award emotional damages, damages must be proved rather than assumed). MCAD decisions are subject to review pursuant to the standards set forth in G.L. c. 30A, § 14 (7), and thus cannot be arbitrary, capricious, or against the weight of the evidence. The MCAD reasonably concluded that, five years after the alleged discrimination, the appropriate remedy was requiring the MBTA to hire Marquez rather than simply engage in an interactive and investigative process in an attempt to accommodate him. The MCAD may have logically concluded that the five-year litigation process sufficiently investigated the extent of Marquez's religious obligations, and the possible avenues of accommodation.

5. Conclusion. In sum, we affirm the judgment of the Superior Court affirming the MCAD's findings of fact and the relief granted. While the MCAD erred when it concluded that the MBTA had violated G.L. c. 151B, § 4 (1A), by not engaging in an interactive process when Marquez sought a religious accommodation, the Superior Court judge correctly concluded that the MBTA made an insufficient showing of undue hardship.

Judgment affirmed.