I don't know if this is supposed to be this way or not, but I'd like to report it just to be sure! Please don't blame me for not knowing.
- The 2x two-way road (placed above the turn road) is placed one level up.
BLOCK 1-3-1
Two-way road turn left (one level up). Perfect!

BLOCK 1-3-2
Two-way road turn left (one level up). You can't place it there!
