30 C.F.R. § 57.14209 – Safety procedures for towing.

(a) A properly sized tow bar or other effective means of control shall be used to tow mobile equipment.
(b) Unless steering and braking are under the control of the equipment operator on the towed equipment, a safety chain or wire rope capable of withstanding the loads to which it could be subjected shall be used in conjunction with any primary rigging.
(c) This provision does not apply to rail equipment.