I hacked a train toilet

My guess is that this is probably the only way, if you also want to support disabled users while ensuring them most agency in the intimate process of using a toilet.

I can see the benefit of the electric opening/closing mechanism, because sliding doors are heavy, but the lock should've been a physical mechanism, or at least acted like one.

The only thing wrong was the fact that they weren't "modern" enough, i.e. too simple and predictable.

That said, you can easily "DoS" a mechanical lock too, if it doesn't have any form of interlock. Everyone who has locked themselves out of cars and buildings (e.g. leaving the key inside) will clearly remember this.

- mechanical cannot be easily unlocked by conductors in case of emergency - mechanical would break more often because people don’t care and would push on door even if it is occupied. - in a hurry might be more convenient to simply push button assuming one is already familiar with the system. - having only buttons it is easier to keep it clean and having people less contact with door handles/latches. - can be automatically locked on stations so people use them between stations so you don’t get foul smells while boarding and waiting

I am told that "superloos" (those automated self-cleaning toilets installed on the pavement) do have some kind of time limit and will play some kind of audial warning a few minutes before opening.

More concerning about those toilets are stories where people somehow managed to be inside the toilet when the self-cleaning process started (which involved the entire chamber being filled with liquid). Supposedly this would happen when someone used the toilet, but held the door open as they left so someone else could use it without paying. The toilet, then thinking it was empty, proceeds to unwittingly try and drown the "undeclared" occupant.

https://www.gableseng.com/wp-content/uploads/2020/05/G7330-....

I am lost for words...

Trains on the other don’t have such minimum staffing requirements and usually operate with only one or two staff total (driver plus maybe a ticket inspector). Train operators want to keep staff on train to an absolute minimum (people cost money after all), but those staff still have some safety responsibilities which can’t be removed. Instead you try to remove every other responsibility they might have, such as dealing with toilets.

Automated toilets means the toilets themselves can be responsible for the vast majority of their operations, and can be trusted to fail safe if something unexpected happens. Meaning there’s no need for staff to perform regular inspections while the train is in service, and no need to worry about something going silently wrong and hurting someone. Instead the toilets can ensure that unsafe situations don’t happen, and proactively alert staff if something unsafe does happen.

I think the original introduction of the button was due to accessiblity. my understanding is that on newer planes they are trying to move towards a similar system for the same reasons.

Buttons flush with the surface or low profile levers such as the ones shown in the picture can be more robust against certain mechanical attacks simply by having lower weight, lower travel, and being smaller (don’t need to exhibit mechanical advantage).

I’m a fan of simple mechanisms with no software in them whenever possible, but I don’t have to deal with the cost and reliability problems.

Sadly all of this adds complexity and more possibilities for failure.

In Switzerland we have bioreactors [1] in newer trains which are like a mini sewage treatment plants. These are still very new and still have bugs that are being worked out such as how much oxygen needs to be provided etc. Until recently it caused a bad smell at the main station which is ironic since that is what we used to have in the 80s with the old dumb toilets.

[1] https://news.sbb.ch/artikel/114447/unangenehmer-geruch-aus-b... (German)

They also auto-close the toilet door when not in use to keep smells away.

And the main reason: Doors aren't really wheelchair friendly - many wheelchair users aren't strong or agile enough to move a door.

With those 3 things to deal with, it's pretty hard to design a mechanical door system that can meet everyone's requirements.

Having said that, the UI could certainly be better. I would personally have had the 'close' button require to be held down the whole time the door is closing. If you release the button early, the door opens again. Only when it is fully closed will it then stay closed and 'locked'. No need for an actual mechanical lock, but there should be a big red padlock light that comes on.

However those don’t work with some passengers - wheelchair users for example, people with difficultiy holding handles etc.

Making toilets more accessible for some groups makes them less accessible for others (. As a society we choose what level to have it at.

Some trains in the U.K. have a good balance - a large wheelchair accessible toilet, and a small traditional one, although they sometimes struggle with communicating it.

Here in Germany, the railway itself is the worst culprit - in December, when DB took over the notorious Hof-Munich line, I travelled on a 6-car double decker train that had 5 broken toilets, all of them because either the water was out or the sewage tank full. Not fun.

The second worst culprits are idiots throwing trash into the toilet. Diapers, tampons and wet wipes don't belong into regular toilets - but especially not into vacuum toilets like on trains or planes.

Of course you can damage or break any physical system if you apply too much force or use it the wrong way intentionally.

In this case, we're talking about a door and a sliding lock. A mechanical design would not have had any of these failure states. All the system needed, was to connect the locking switch to the physical door lock, and none of this would've caused a problem.

If you're automating something as simple as a door lock, you need to be able to deal with this stuff. If you can't, stick to what works instead.