30 CFR 57.20011 - Barricades and warning signs.
Areas where health or safety hazards exist that are not immediately obvious to employees shall be barricaded, or warning signs shall be posted at all approaches. Warning signs shall be readily visible, legible, and display the nature of the hazard and any protective action required.
Title 30 published on 2013-07-01
no entries appear in the Federal Register after this date.