30 CFR § 56.3430
Activity between machinery or equipment and the highwall or bank.
Persons shall not work or travel between machinery or equipment and the highwall or bank where the machinery or equipment may hinder escape from falls or slides of the highwall or bank. Travel is permitted when necessary for persons to dismount.
Subpart C--Fire Prevention and Control
AUTHORITY: § 101, Federal Mine Safety and Health Act of 1977, Pub. L. 91-173, as amended by Pub. L. 95-164, 91 Stat. 1291 (30 U.S.C. 811).
For further information: See MSHA's Program Policy Manual