Cal. Code Regs. tit. 8, § 7023 – Industrial Railroads.

(a) (9-83) The tracks for all industrial railroads in use in the mine or on the surface shall be kept in good condition, free of dips, bumps, or obstructions that may interfere with safe operation of haulage equipment. Surface industrial railroads and clearances shall comply with the Industrial Railroad standards of the General Industry Safety Orders.
(b) All bridges and trestles shall be substantially constructed and maintained in good repair. They shall not be subjected to loads greater than they were designed to support.
It is recommended that bridge and trestle timbers be treated with an effective preservative before being used.
(c) (9-20) Positive-acting stopblocks, derail devices, track skates, or other adequate means shall be installed wherever necessary to protect persons from runaway or moving railroad equipment.
(d) (9-28) Switch throws shall be installed so as to provide adequate clearance for switchmen.