((a)) ** .—** This chapter does not apply to a situation involving any of the following:

((1)) a casualty.

((2)) an unavoidable accident.

((3)) an act of God.

((4)) a delay resulting from a cause unknown and unforeseeable to a railroad carrier or its officer or agent in charge of the employee when the employee left a terminal.

((b)) ** .—** The Secretary of Transportation may exempt a railroad carrier having not more than 15 employees covered by this chapter from the limitations imposed by this chapter. The Secretary may allow the exemption after a full hearing, for good cause shown, and on deciding that the exemption is in the public interest and will not affect safety adversely. The exemption shall be for a specific period of time and is subject to review at least annually. The exemption may not authorize a carrier to require or allow its employees to be on duty more than a total of 16 hours in a 24-hour period.

((c))

((1)) When providing commuter rail passenger transportation or intercity rail passenger transportation, the limitations on duty hours for train employees of railroad carriers, including public authorities operating passenger service, shall be solely governed by old section 21103 until the earlier of—

((A)) the effective date of regulations prescribed by the Secretary under section 21109(b) of this chapter; or

((B)) the date that is 3 years following the date of enactment of the Rail Safety Improvement Act of 2008.

((2)) After the date on which old section 21103 ceases to apply, pursuant to paragraph (1), to the limitations on duty hours for train employees of railroad carriers with respect to the provision of commuter rail passenger transportation or intercity rail passenger transportation, the limitations on duty hours for train employees of such railroad carriers shall be governed by new section 21103, except as provided in paragraph (3).

((3)) After the effective date of the regulations prescribed by the Secretary under , such carriers shall—

((A)) comply with the limitations on duty hours for train employees with respect to the provision of commuter rail passenger transportation or intercity rail passenger transportation as prescribed by such regulations; and

((B)) be exempt from complying with the provisions of old section 21103 and new section 21103 for such employees.

((4)) In this subsection:

((A)) The terms “commuter rail passenger transportation” and “intercity rail passenger transportation” have the meaning given those terms in .

((C))   The term “new section 21103” means section 21103 of this chapter as amended by the Rail Safety Improvement Act of 2008.

((D)) The term “old section 21103” means section 21103 of this chapter as it was in effect on the day before the enactment of that Act.