Cal. Code Regs. tit. 8, § 7133
(d) To prevent employees from being caught between the moving shaft conveyance and the shaft walls, chute lips, timbers, or other obstructions, one (1) or more of the following precautions shall be taken:
(1) At least 2 feet of overhead clearance shall be provided between men on the shaft conveyances in their riding position and the nearest shaft wall, chute lip, timber, or other obstruction.
At least 1 foot of clearance shall be provided between men on the shaft conveyance in their riding position and the nearest obstruction at the side of the shaft conveyance.
Note: The chief hazards of hoisting and lowering men in inclined shafts are derailing the shaft conveyance, breaking the hoisting cable, falling rock or materials, and striking against fixed objects.