In the tutorial I see how to make a road like the TLA-5. My question is how do you make any curves or turns in that type of road and keep the center turn lane?
At this point, you can't. As noted in the readme, currently, every dual-tile network in the NWM is orthogonal-only and does not have any ability to go diagonally or curve. That functionality is planned to be integrated in a future release, though it is unclear just when.
-Alex