A person may not, individually or through an agent or employee or as an agent or employee, operate covered equipment in the proximity of an overhead high-voltage line unless there are posted and maintained warning signs as follows:
1. In covered equipment. A sign must be located in the covered equipment and readily visible and legible to the operator of the covered equipment when at the controls of the covered equipment; and
2. Outside covered equipment. Signs must be located on the outside of covered equipment in numbers and locations that are readily visible and legible at a distance of 12 feet by people engaged in the work operations.