If you ever had a question about UniDirectional Networks (UDoNs), this is the place to go. Here contains many of the tips, tricks, and primary mechanics of the mod.
Core Mechanics Edit
(You can skip this, but you might want to come back!)
All UDoNs technically have a median which you don't see.
This is technically the reason why 3-lane one-way roads aren't made yet: there is no moddable way to make cars travel on medians.
Elevated and transition highways work with a modified form of MagLev where only vehicles like cars are allowed on it.
Due to how the game registers MagLev vehicles, there is a chance that MagLev trains can appear on elevated highways. To solve this problem, use the road upgrade tool, and select the "Disable Connectors" option.