When multiple toilets exist, keep left/right consistency across the building
Friction: Don't mirror layouts blindly; habit matters.
Why this matters
If the men’s room is on the left on the 1st floor, it should be on the left on the 2nd floor. “Mirroring” layouts for plumbing efficiency often confuses users who build a mental map of the building.
Good Sense principle
Respect the user’s mental model. Predictive environments are stress-free environments.