Not later than 18 months after the date of enactment of this Act [Dec. 4, 2015], the Secretary [of Transportation] shall initiate a rulemaking to require that on-track safety regulations, whenever practicable and consistent with other safety requirements and operational considerations, include requiring implementation of redundant signal protection for maintenance-of-way work crews who depend on a train dispatcher to provide signal protection.

The Secretary shall consider exempting from any final requirements of this section each segment of track for which operations are governed by a positive train control system certified under section 20157 of title 49, United States Code, or any other safety technology or practice that would achieve an equivalent or greater level of safety in providing additional signal protection.”