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Public Restroom Doors are a Nightmare

· 5 min read

Look at this. This is the interior handle and lock of a single occupant public restroom door. Someone spent a lot of time and effort creating what might be the worst lock imaginable.



This is the interior of an airplane restroom. Whoever designed this door understood the assignment.

airplane door lock


A restroom door needs to do three things:

  1. Prevent anyone from entering when there's an occupant
  2. Make the occupant feel like no-one will be able to enter (otherwise it's stressful)
  3. Prevent people from having to attempt to enter to find out if there's an occupant

You'd think, considering how many of these damn doors have been built that this would be a thoroughly solved problem, but in my experience it's genuinely rare to find a door that correctly and consistently does all 3.

It was a level 1 failure that motivated this blog post.

A door like this is composed of several systems. It has:

  1. Hinges that allow it to open and close
  2. A latch that prevents it from opening
  3. A knob that disengages the latch
  4. An exterior lock that serves an authorization check (i.e. someone will size you up and decide if you deserve the code to the bathroom)
  5. An interior lock that's operated only by the occupant

Any of these systems could be omitted (except the hinges and interior lock), and they often overlap.

airplane door lock

Whoever put up this "look" sign knew there was a problem here, but didn't know what it was

Failures happen because human beings have to operate these systems without necessarily knowing which ones are preset, how they work, or what the state of each system is.

Sometimes the systems are bad, but more often the problem is the signals. That handwritten "look" sign assumes people aren't looking at the locked/unlocked indicator before trying to enter. But the are looking; they're just assuming it's an indicator for the exterior lock, not the internal lock. There are three locks on this door after all. The "look" sign appeared a few weeks before the authorization lock got taped over in what I assume is just further desperation in trying to deal with this bad design.

It's not trivial to signal each of these systems correctly, but there's really only one that matters; the interior lock. And the state of this lock needs to be signalled clearly on both sides of the door.

In 2026, the year of our Lord, humanity has managed to solve half the problem (or at least that's where the U.S. is at. This might be better elsewhere). There is often a sign on the door exterior like this:

vacant lock

Explicitly "there is someone in here" and you can't miss it.

Here's the interior of the same door:

interior lock

An employee had the sense to tape up a little sign to at least show the direction to turn the lock, but at what point is it locked? How will you know? Can you at least test that it's locked?

I nearly walked in on a little girl using this very restroom. The only thing that saved us both was a slight hesitation on my part after cracking this door (with a giant VACANT sign on the front, mind you) due to some dim memory that this lock catches early, just like the one in the first video. Nearly had to start my day at the coffee shop trying to explain to some furious parent why we don't need to call the police.

There are layers to how bad this design is.

  1. Any slight misalignment in the door causes the lock to catch before it's actually locked.
  2. There's no indication at all if the lock is properly locked. It's locked at "arbitrary degrees turned", and that's knowledge you don't have.
  3. Turning the handle unlocks the lock, so YOU CAN'T EVEN CHECK THAT IT'S LOCKED.

At this point, the vacant/occupied sign is a liability, because it tells the person on the outside "hey there's definitely no one in here, walk right in". If your goal was to create the most evil restroom door possible, you could not have done better than this.

interior lock

Cheap, low tech, and unfortunately forces the "have to try opening the door to find out if someone is in here". But it won't fail, and it's completely clear to the occupant when it's locked.

I don't know what it is about public restrooms. The doors, the stupid motion-sensing sinks and towel dispensers, and oh god the stalls. It's an essential part of life in public and I don't understand why we don't get it right.