咸北線
The third stage of the Pukbunaeryuk Line project was to have been the construction of a new line from Musan to Hoeryŏng on the Hambuk Line. From Musan, the line was to have run through Musan County along the Tumen River via Ch'ilsŏng-ri and Saegŏl-li, continuing from there along a newly built line to Yusŏn, the terminus of the Hoeryŏng Colliery Line; this line would have been absorbed into the Pukpu Line.