The "Teddy Roosevelt" road is really just a federal right of way, and in most of NM there is NO road, and lots of miles of terrain so rough you could not drive along it if you wanted to. Also at least here in NM it is treated as a federal right of way only and the public at large has no right to travel there. The majority of NM border is the perimeter of a very few large ranches that are entirely closed to the public, and they enforce trespass laws against anyone found on the ranch. There are no gates to access only the border fence, and if you were not a government official they would charge you with trespassing for attempting to drive along the border fence.
I don't know how it is in CA, AZ, or Texas, but that is how it is here. We could ask each rancher how many miles of fence are on their ranch, but my hubby has worked on several of these big ranches and he already knows the answer. The whole border here is just pasture fence, it is maintained by the ranchers, just for the purpose of keeping livestock in, and it all is really old.
NM is totally fenced with pasture fence, there are only three ports of entry in NM; Antelope Wells, Columbus, and Santa Theresa. Antelope Wells has pasture fence even at the port, there is not even a Gov't fence on the port property, just pasture fence. There is a fence planned for the port property itself, but there is not one there now. Columbus POE only has a tiny piece of Chain link at that POE, same at the Santa Theresa crossing.
If you figure out the miles of border fence in NM and deduct 1 mile total for Gov't fence at the ports you would be generous in deducting the mile. There is NO part of the border that has any type of fence other than pasture fence in NM other than small pieces at the ST and Columbus POEs.
Hubby estimating 170 miles in NM, but you could get a much closer figure by getting an accurate map and measuring on the map.