49 C.F.R. § 213.11
If during a period of restoration or renewal, track is under traffic conditions and does not meet all of the requirements prescribed in this part, the work on the track shall be under the continuous supervision of a person designated under § 213.7(a) and, as applicable, § 213.7(c) . The work on the track shall also be subject to any limiting conditions specified by such person. The operating speed cannot be more than the maximum allowable speed under § 213.9 for the class of track concerned. The term "continuous supervision" as used in this section means the physical presence of that person at the job site. However, since the work may be performed over a large area, it is not necessary that each phase of the work be done under the visual supervision of that person.
49 C.F.R. §213.11