29 CFR § 1917.16 - Line handling. (See also § 1917.95(b)).
(a) In order to provide safe access for handling lines while mooring and unmooring vessels, cargo or material shall not be stowed or vehicles placed where they obstruct the work surface to be used.
(b) When stringpiece or apron width is insufficient for safe footing, grab lines or rails shall be installed on the sides of permanent structures. (“Stringpiece” means a narrow walkway between the water edge of a berth and a shed or other structure.)