The Nürburgring is a private road and does not meet criteria for calling it an Autobahn (it's a one-way road without lanes, which kinda rules out Autobahn-ness).
It’s a closed toll road with two lane one way traffic but without markings. Overtaking only on the left, after overtake one should go back to the right. There’s no such thing as racing line. There are a couple of speed limits: 70kph by the exit in Breidscheid and 120kph on the Döttinger Höhe, before exit to the Touristenfahrten car park (going down to 50kph right before the exit).
During Terroristenfahrten, regular traffic rules of a two lane single direction road apply.
