30 CFR § 56.9100
Traffic control.
TRAFFIC SAFETY
To provide for the safe movement of self-propelled mobile equipment
(a) Rules governing speed, right-of-way, direction of movement, and
the use of headlights to assure appropriate visibility, shall be established
and followed at each mine; and
(b) Signs or signals that warn of hazardous conditions shall be
placed at appropriate locations at each mine.