; (B) locomotives performing assistance to a train that has incurred mechanical failure or lacks the power to traverse difficult terrain, including traveling to or from the location where assistance is provided; (C) locomotives that— (i) are not attached to any equipment or are attached only to a caboose; and (ii) do not travel father than 50 miles from the point of origin of such locomotive; and (D) train operations staffed with fewer than a 2-person crew at least 1 year before the date of the enactment of the Safe Freight Act of 2023 unless the Secretary determines that such operations do not achieve an equivalent level of safety as would result from compliance with the requirement under subsection (a). (2) Trains ineligible for exception The exceptions under paragraph (2) may not be applied to— (A) a high-hazard train (as defined in section 20155(a))