(a) The owner, agent, lessee, bailee, user, or employer responsible for the operations of equipment capable of coming within dangerous proximity of a high-voltage line in the course of its operation, shall post and maintain in plain view of the operator on each piece of such equipment, an approved durable warning sign legible at a distance of 12 feet. Every such warning sign shall bear the following legend in black letters on a yellow background:

(b) All posted warning signs shall specify the actual distance by which the term “dangerous proximity” is defined for the particular case and location to which this Part (rule) applies.

(c) Additional warning signs shall be placed on various parts of the equipment and at the work site providing similar warnings to others in the vicinity of the high-voltage lines.

(d) If for any reason and for any time period, the operator of the equipment is unable to assess visually the clearance of the equipment from overhead high-voltage lines, a second person shall be designated to observe the clearance and provide timely warning to the equipment operator.