The Nether Highways are roads in the nether at y = 120. There are 4 highways that go in each direction and they all originate at 0,0. There are also smaller but safer diagonal highways. The Highways are built and maintained by SIG.
The X+ highway is the longest, stretching out as far as 3,750,000 blocks. There are numerous monuments alomg the way, however most if not all of them are griefed. At the end of the highway is Point Nemo. The +X highway was completed by the Nether Highway Group March 3rd 2017.
The X- Highway is a nether highway that stetched eastward. There are also numerous monuments along this one. It was completed December 22nd 2017 by Metrez and his highway group.
The Z+ Highway is the highway that goes southward, and links up with the Southern Canal in many places.
The Z- highway stretches northward, it is the shortest highway and only goes to about 2 million nether.
There are shorter, but less used diagonal highways that go Northeast, Southeast, Northwest and Southwest.