Safety recommendation
Philadelphia Electric Company Notified to Install Spherical Markers on Transmission Lines
Federal Aviation Administration recommends markers on river-crossing transmission lines.
The Federal Aviation Administration has advised the Philadelphia Electric Company to mount spherical markers that conform with Advisory Circular 70/7460-1G on transmission lines crossing the Susquehanna River near Airville, Pennsylvania, and on other transmission lines that cross rivers, lakes, canyons, or gorges. The recommendation is part of aviation safety guidelines to enhance visibility of such structures.
Original regulatory source: https://data.ntsb.gov/carol-main-public/sr-details/A-89-099