How would you show this situation: If you enter the garage though the auto entrance on the west side in the illustration and go straight ahead, you will descend a level. The mapped "wall" straight ahead of you (indicated by purple arrow) isn't really there... but if you go down, you won't be on the same level as the exit on the opposite side. The reverse happens if you enter from the east and go straight ahead, you will go up one level and be unable to exit.
If you enter the garage from east or west and wish to pass through and out the other side, you must go left or right; going straight ahead takes you to a different level.
So, do you just show the imaginary wall mid-way on the ramp? Or is there some other symbol you can add to indicate that a runner proceeding straight would go above or below?