Typically, the stall closest to the door in a public restroom is the
cleanest, while the middle stall is the dirtiest.

Public restrooms can often seem like a "perfect storm" for spreading germs.
E. coli, salmonella, coliform, rotavirus and even MRSA, the potentially
deadly staph bacteria, could be lurking anywhere. But when you've got to
go, you've got to go, even if it means using a public bathroom. At least
germaphobes can now take comfort in a study that says the stall closest to
the restroom door is usually the cleanest.