
The hotel bathroom puzzle - tlrobinson
https://nevalalee.wordpress.com/2015/11/27/the-hotel-bathroom-puzzle/
======
jasonkester
I'm reminded of a discussion we had here a few weeks ago, where somebody noted
that humanity wouldn't be able to invent, for example, a machine to
automatically rack pins at a bowling alley today.

The 2018 solution to that problem would automatically involve computer vision,
AI and robotics. The idea that one could construct a giant mechanical device
the size of an entire bowling lane that is purpose built to lift, sweep,
collect, rack, and place pins with no capacity for customization whatsoever
wouldn't even occur to today's generation of engineers.

You can see it happening in some of the comments here.

~~~
StavrosK
Have today's engineers somehow stopped believing that the simpler thing is the
most useful? Or is it that writing some code to glue together off-the-shelf
parts is cheaper and easier than designing and manufacturing a giant machine?

~~~
lmm
> Have today's engineers somehow stopped believing that the simpler thing is
> the most useful?

Simplicity is a means to an end. There's no point in a "simpler" solution if
it's more expensive and harder to maintain.

> Or is it that writing some code to glue together off-the-shelf parts is
> cheaper and easier than designing and manufacturing a giant machine?

Exactly.

Good engineering is about meeting the client's needs, not about showing off
your own virtuosity. Too many on HN seem to forget that.

~~~
henriquemaia
I would argue that if a solution is more expensive or harder to maintain, it
is not _simpler_. Teleologically speaking, being _simpler_ is a bigger
umbrella which covers many facets of the intended solution.

~~~
Dylan16807
I don't think "more expensive" is a valid criterion. When you replace a big
chunk of metal with 20 carefully-designed parts that come out to be a third of
the price, you have not made things simpler.

Even if it comes out as equally difficult to maintain.

------
acranox
This sort of goes to something I learned as an auto mechanic. When you have a
problem, describe the symptoms as objectively as possible. Don’t say, “I need
my tires balanced.” Or you might get your tires balanced but the problem
persists. Instead say, “I feel a vibration when driving on the highway at
60mph.” This forces the technician to diagnose the problem.

That’s an overly simplistic example but that’s the point. Tell your doctor
what your symptoms are, without including statements that suggest a cause, or
otherwise limit the scope of the issue.

~~~
duxup
First step of any technical support case, or just troubleshooting anything is
"Define the problem" and that includes when it happens, the circumstances, the
circumstances when it doesn't happen, and etc.

One of my first real jobs I quickly became the favorite of some folks on the
engineering team. The thing was I was not experienced, I didn't know much, but
I followed a simple formula to write up problems, and they liked that. I often
missed some basic steps and didn't have experience, but for whatever reason
they liked how I gave them information. Also when they asked a question I was
very clear and honest with "I don't know" and "I'll find out".

Other smarter techs would make assumptions based on their experience, fiddle
with this and then, and then present to engineering this rambling tale that
was all about what they tired to fix the problem and didn't fix it.... all
while missing what the problem was in the first place, when it happened, and
so on.

~~~
matt_the_bass
Not only tech support but also sales.

When I attend trade shows, I often have potential customers come and ask if we
sell a particular type of technology. I’ve discovered that really what they
are doing is asking if we sell the think they they _think_ is the solution to
what they _think_ is the problem. It’s my job to figure out what their problem
_actually_ is and then figure out if we have something that can solve _that_
problem.

One has to be quite diplomatic in these situations. They certainly know more
about their domain, but I know more about technologies to solve their problem.
So I need to pry out more information without sounding like I think I know
more about their job than they do.

I like that part of the job.

~~~
wool_gather
Nice; the generalized version of "if I'd asked my customers what they wanted,
they would have said a faster horse".

------
rjtobin
I visited some dorm rooms in Croatia once, and they had a nice solution to
this problem. Both doors opened inward, with the non-hinge side of the doors
sitting very close to one of the walls with no doors. Instead of a
conventional lock, a narrow piece of wood ran the length of this no-door wall
that could be rotated to block both doors simultaneously.

This is like the solution in the article, except deals with the "opens-
inwards" case instead of the "open-outwards" case, and is less fumble-y than
having to attach a rope to both doors.

~~~
talldan
I've seen a similar solution in the swimming pool changing cubicles at a
Center Parcs in the UK. The cubicles have two inwards opening doors opposite
one another. Once inside, you close both doors and fold down a bench which
blocks the doors shut and gives you somewhere to sit. Very clever solution.

~~~
whatsstolat
Except if there is a fire and you realise it's stuck. A normal lock can be
kicked in if not opened with master key, but that contraption sounds hard to
break in to.

~~~
craftyguy
I feel like a fire at a swimming pool might be more rare than a fire
elsewhere, just by virtue of being surrounded by water (pool, showers, etc).
Maybe I'm wrong.

~~~
whatsstolat
True. You might get smoke from somewhere else in the building though.

------
userbinator
In other words, the bathroom is a "critical section" and instead of focusing
on locks on each door, it's been replaced with one big "lock" that locks them
all at once.

~~~
brudgers
It makes the transaction atomic.

~~~
cryptonector
You can do that with two locks too, but one is simpler.

Also, there is a failure mode here. Can you think of it?

~~~
bdamm
Death of the person in the bathroom? Damage to the hooks causing a jam or
releasing the lock entirely? Simply not engaging the lock at all? Someone
walking off with the thong and using it creatively elsewhere in their hotel? A
few failure scenarios. Nothing's perfect!

~~~
cryptonector
Death or incapacitation of the person in the bathroom is what I had in mind.

Yes, there's also the leather strap or hook (or doorknobs, ..) breaking. I
hadn't considered that, oy.

------
wool_gather
Awesome solution, simple genius. So many times I've tried to explain a similar
principle for this kind of situation. Signs don't work! People don't read them
(actually, they often don't even _see_ them, at least consciously). Especially
when it's a common action. You generally have to physically alter their path
through the task to get their attention -- disrupt the affordances somehow.

If you don't want anyone to turn on the oven, _cover the knob_ (or remove it).
Same for a door handle. There's one case of something on the shelf that's
earmarked for a particular purpose? Tie or tape it in place. A sign works to
give reasoning, but first you have to slow down the distracted and goal-
oriented person enough to read it.

Another good example of this kind of design is circuit breaker lockouts: an
electrician needs to work on a particular circuit, so they turn off the
breaker. To make sure that no-one turns it on and kills them while they're
still working, they bar the switch in place with a physical lock that only
they have the key for. Better, some models allow multiple locks to be attached
(it's like a physical concurrency semaphore). Then the circuit can't be re-
powered until _all_ locks have been removed.

------
LeoPanthera
A surprising number of these comments are trying to find problems with the
solution.

I've noticed a tendency for hackers to assume that practical solutions to real
world problems are theoretical, and then try to pick holes in them, forgetting
that if the solution is already implemented and in place, then it probably
works just fine.

~~~
dvdkon
But that’s a big part of designing anything: Trying to find a solution’s
faults to then be able to implement a better one or at least be aware of the
faults and work around them. I don’t see anything wrong with that.

~~~
jdbernard
To echo you, that's also one of the things you painfully learn when working
with real software systems: there will always be failure cases you didn't
think of. Better to catch as many as possible early. Just because it's working
_now_ doesn't mean it will keep working tomorrow.

------
foxhop
When I was a young child I tied the pantry light's pull chain to string and
tied the string to the door handle, just taut enough that it would enable the
light when the door was opened.

Regretfully to shut the light off, I needed to first close the door, re-open
the door and then finally close it.

~~~
hyperdimension
Crafty. I like it. It's funny the little (and not-so-little) things we put up
with, just so we can bask in the joy of our own creations.

------
Jaruzel
As everyone else is trying to re-solve this problem in a better way... Here's
my 2p's worth:

Employ a monkey to lock/unlock both doors for you. Use something like a banana
for lock and an orange for unlock, keep baskets of both fruits in the
bathroom. To stock the baskets get the maids to do it when they change towels.

~~~
King-Aaron
I would pay good money to stay at a hotel that utilises monkey-lock-fruit-bowl
arrangements

~~~
cwkoss
One ticket for the lockpicking monkey circus please

------
sampl
In product management this is often described as problem space vs solution
space.

One of my biggest lessons in “managing up”: agree on the problem, and take any
suggestions for a solution seriously. Then work to make the solution you
present as good or better.

~~~
chii
> often described as problem space vs solution space .... agree on the problem

The hard part being agreeing on the problem!

Sometimes, management sees the "solution", and present it as a problem that
engineers then must solve. For example, competitor has brand new feature, and
management asks said feature to be implemented (presumably, keeping up with
the jones style). But the actual problem isn't lack of said feature, but that
customers are not buying, and the only reason that's presented is a lack of
said feature.

------
jf-
I’d find it rather difficult to use a bathroom that was divided in half by a
leather thong.

~~~
esturk
Why, because of the string thru the room? It can be placed along either side
of the wall.

~~~
michaelmior
I have trouble seeing how it could be placed along the wall while maintaining
the necessary tension.

~~~
StavrosK
Through rings bolted to the wall.

~~~
michaelmior
Good (and in retrospect, obvious) point!

~~~
StavrosK
Yeah, I misunderstood things worse: I thought doors opened inwards, and that
the ropes were somehow rigid (basically rods).

------
georgyo
The bathroom connects two rooms where you don't know or trust the other room.

Without a lock you have no way to prevent them coming into your room when you
are not there.

Still that is some great out of the box thinking.

~~~
joshuahutt
That thought occurred to me, too, but I realized that you could add locks that
could only be locked from the bedroom sides.

~~~
zackkatz
Yes, but then the problem becomes possibly being locked out of your own
bedroom, stuck in the shared bathroom!

~~~
radicality
How? If someone from your room on purpose locks you in the shared bathroom?
That doesn’t sound like a likely scenario

~~~
redsparrow
I lived in on-campus student housing that had bathrooms like this (the locks
on both sides of both doors version.) My friend was in the bathroom during a
commercial break of X-Files and I locked him in there. Ha ha. So he knocked on
my neighbour's door and got out that way, but he still needed to get back into
my room from the public hallway. I was watching him through the peep hole in
my door, and to taunt him I opened the door and quickly closed it again. The
two problems with that were that the peep hole made it look like he was
further away than he was and the door had a hydraulic arm on it and didn't
close as quickly as I expected. Anyway, I put ice on my forehead for the rest
of the episode and then went to the hospital for three stitches.

I'd say that the likeliness really depends on whose bathroom it is. ;)

------
ghostly_s
> You could, of course, tear down and rebuild the entire hotel, at great
> expense, so that each room has its own bathroom—a solution that might sound
> ridiculous, but isn’t so far removed from how similar design problems are
> addressed every day.

The 'similar design problems' link in this sentence points to an article about
how the video game Destiny was delayed due to a story re-write. What on earth?

------
farss
I was at one of the baths in Budapest recently where I saw another solution to
this problem. The locker room is mixed gender, and the changing stalls have
two doors that open to opposite sides of the aisle. But the doors open inward,
and the bench inside folds down to block them while occupied. Then you have to
lift the bench to get out.

------
madcaptenor
I thought this was going to be about the question of why every hotel bathroom
has a different way of controlling the hot and cold water in the shower, and
why none of these are anything like what you see in most residential
bathrooms.

------
yardstick
No one has mentioned this yet: remove the two private doors and install a
single door in the common hallway.

Yes you lose some convenience by having to be clothed while entering and
exiting the bathroom. But at least you guarantee the door is always unlocked
when not in use.

~~~
user5994461
That's only possible if the bathroom is next to the hallway, otherwise they
have to tear down the building.

------
jamesfisher
Some parts of the solution are left unspecified. Which way do the doors open?
Surely not inwards, else someone can intrude. Do they only open outwards? In
which case, to get out, does the leaver first detach the rope from the
handles?

~~~
PeterisP
Realistically, if you're the one solving the problem, then the answer to
"Which way do the doors open?" is "whichever way you want, since it's _you_
who decides on how to build them".

------
yitchelle
I guess if society had no problems with nudity and bath room activities, the
problem of needing to keep the doors locked when it is occupied not exists.

~~~
roddds
I have zero problems with nudity and I still don't want anyone walking in on
me while I'm taking a dump.

------
FrozenVoid
Instead of relying on the user to "do the right thing", the idea is to prevent
the user from doing "the wrong thing" and making it as automated as possible.
This is course clashes with the "let the user freedom to do anything", forcing
subpar decisions and predictable mistakes. Making the interface of system
simple is more important that making the system itself simple.

------
blt
The bathroom in my house is like this. This solution would make me happy, but
perhaps is too weird to be worth explaining to visitors.

~~~
chii
I'd imagine visitors would marvel at the succinctness of the design, and it'd
be a talking point!

~~~
SmellyGeekBoy
Unless they're HNers, in which case they'd take great delight in demonstrating
their superior intelligence by explaining why your locking system is
ineffective due to various hypothetical scenarios.

~~~
other_herbert
Or attach the lock mechanism to the toilet so when a door is opened it flushes

------
vagab0nd
I get what the author is getting at. But this particular example doesn't
really help with the conclusion. The solution is still about locks, just that
the 2 locks are now linked together.

~~~
TeMPOraL
There are no locks in doors at all. There is a single mechanism physically
connecting the doors together, so that neither can be opened, and that can
only be engaged and disengaged from the inside.

~~~
amalcon
How is that mechanism not, itself, a lock? It's an unusual (and well suited)
kind of lock, sure, but still a lock.

~~~
JdeBP
Try pointing to the part that is the key that unlocks it, and you will see.
(-:

Yes, strictly speaking the headlined article is likely talking about _door
bolts_ not locks.

~~~
amalcon
There are plenty of locks that do not use keys, e.g. a keyless deadbolt.

~~~
JdeBP
No. The key that unlocks a "keyless" deadbolt is the code that one types in.

~~~
amalcon
That type exists, yes. There is also the variety that is simply impossible to
unlock from one side.

------
arikrak
Another way would be to make the the lock a large rotating latch that was
connected mechanically to a similar latch on the other side.

While this would be more complex, it wouldn't get in the way as much.

~~~
krallja
Another possible solution:

Each side has two locks: one that is locked when the key is missing, and one
that is locked when the key is present. To give yourself privacy, you must
also lock yourself in. To exit the room, you must first unlock the other door
and use the key to unlock your own door.

~~~
pzh
It’s also asymmetrical. The occupant of the locked-when-key-is-present room
would have no incentive to return the key and to unlock the opposite room
door.

~~~
krallja
It’s not really assymetrical: both sides have one key and two locks. But
you’re right that it won’t work.

------
sriram_iyengar
Brilliant ! Means vs End. Getting fixated and not taking a step back only adds
more debt to the solution, if the problem is partially solved.

------
King-Aaron
I'd have assume the door handles are close to a blank/empty wall... Otherwise
all I can imagine is trying to use various things in the bathroom and having
to step over a waist-level leather strap running through the middle of the
room while you're trying to use it.

As the diagram goes at least, if you were sitting on the toilet, and then
decided to have a bath, you'd be contorting yourself over the strap.

------
aj7
This entire treatise presumes not using one switch, two locks. Cars seem to
have no trouble with this.

~~~
bdamm
Electronic locks was not a thing in 1900. Old cars with manual locks did
indeed have the cases where the driver reaches over and locks the passenger
door, when the passenger forgets to lock it themselves. And users of old cars
will remember the "open front door, reach inside and unlock back door"
maneuver.

~~~
KayEss
Central locking: if you're in the centre of the car yu can lock all the doors.

------
cryptozeus
Someone attaches the rope and dies in the bathtub. Now we have a problem ...

------
skepticmoron
You can use sensors to figure out if someone is inside these days. Tech is
cool.

~~~
panic
The sensors have a lot more failure cases, though, and it can be hard to tell
whether they're working properly.

~~~
macintux
Reminds me of light sensors in bathrooms. Often you have to wave your arms to
let the sensor know you’re still inside.

~~~
panic
Yeah, that's what I was thinking of too. Don't relax in the tub too long or
the doors will unlock!

~~~
jessaustin
That could be a feature, for someone waiting to use the facilities...

------
basicplus2
could also use a mechanical interlock such that when one door opens, it locks
the other door, then when you return to your room the act of closing your door
behind you unlocks the other door.

------
tamaharbor
Wouldn’t this make it easy to get into the adjacent guest room?

~~~
mcphage
They could still have locks on the doors, but the locks would be to keep
people out of the hotel rooms, not out of the bathroom.

~~~
michaelmior
I believe the parent is suggesting that the two rooms adjoining the bathroom
would be mutually accessible when they shouldn't be.

~~~
joshuahutt
Yes, so you have a lock on the door that you can only manipulate from your
room. Unlock it when you need to use the bathroom, lock it otherwise.

~~~
michaelmior
This of course doesn't allow you to lock the bathroom when you're in it from
other people also in your hotel room. Although this is certainly much less of
a concern.

------
coherentpony
What if both doors don't open in the same direction?

------
bahmboo
Sure, but what if both doors open _into_ the bathroom?

~~~
bradlys
Oh. I get how the solution works now. I was assuming the doors opened into the
bathroom (which I think most do in most places I've been??).

If they open into the room then you have two giant rods that you connect
together to hold them shut? Another solution but even weirder...

------
fireattack
>where bathrooms share a bathroom

Is this a typo?

~~~
m_herrlich
In the Hotel Louis IV even the bathrooms have bathrooms (but the guests still
have to share)

------
opdahl
Very interesting problem! The supplied solution is simple and it works for
that specific use case, but there are still some problems.

1) This can only be done where its feasible to connect the two doors with a
rope. What if the doors are physically seperated far away from each other, or
maybe even seperate entrances to a large bulding complex?

2) You can be locked inside the bathroom if someone locks the door behind you.

So i tried coming up with my own solution to solving the specified problem
while also dealing with the problems with the other solution.

First off it makes sense having a system with keys and devices that are easily
installed at each door. That way you deal with problem 1.

With this solution another problem arises: You can just remove a key from the
room and nothing will work, so a constraint is introduced.

Specifically: It should be impossible to exit the room while carrying any of
the keys, given you don’t work together with the opposite side.

So my solution is: A connected sliding lock on both sides of both doors, plus
a sliding lock containing a key on both doors inside the bathroom. So one
sliding lock in the apartment side and two locks the bathroom side for each
door. Inside the bathroom you can only lock the opposite sides door by locking
your own door first. Locking your own door with the sliding lock containing a
ley gives access to the key which you insert into one of the sliding locks on
the opposite side. An important feature is that you can not remove the key
from the lock on the opposite side without first unlocking it and you can not
unlock your own door without using the key.

So with this system it is impossible to leave with a key from the bathroom,
and you also can’t lock your opponents door without locking your own door,
barring your escape.

At first I thought this solution was the perfect one, but then I realised that
there is nothing stopping someone from stealing the key from the opposite side
by just locking the opponent door with their sliding lock, removing the key,
and leaving the room.

The solution to this is that the sliding lock for eachs side key is connected
to the sliding lock on the apartment side. By this I mean that when the door
is locked on the apartment side, it will make the sliding lock on the bathroom
side unmovable, and aldo vice versa. If you have locked the door on your side,
the sliding lock will also be immovable. This way nobody can lock you inside,
and you can not steal the opponents key because it is locked from its
apartment side therefore blocking the use of the sliding lock with the key on
the bathroom side.

So I think this solution works, even though it is somewhat complicated. So
heres the user story for using the bathroom.

1\. Unlock door on apartment side. 2\. Lock door on bathroom side, and take
key. 3\. Use key to lock door on opposite side 4\. Do your business 5\. Unlock
opposite side, and take key 6\. Use key to unlock your own door, locking the
key in place in he process 7\. Exit the bathroom and slide the lock again.

I guess this is what you would call «over-engineering» but it was fun trying
to come up with a solution!

Please tell me if I’ve missed something that would break this, I can’t come up
with anything atm.

------
IshKebab
Has nobody ever been swimming?

~~~
megablast
I have never seen this situation at a swimming pool, and I have no idea why it
would be necessary at all? Just have a cubicle with a shower curtain, or an
ordinary change room.

~~~
IshKebab
All swimming pools in the UK have cubicles with two doors - one that leads to
the pool and one that leads to the exit. There isn't any way around the
cubicles.

It's to prevent people casually walking into the pool in shoes and making it
dirty.

They use a single piece bar that locks both doors simultaneously.

------
king_nothing
If only London hotels architects had known this, the majority of showers might
not be a size smaller than a phone-booth such that you cannot turn around in
it and must enter/exit sideways... while not being at all rotund.

------
sorokod
So: try { lock() } finally { unlock() }

------
cryptonector
Ah, but there is one failure mode... Can you find it?

~~~
cryptonector
Guess not. The failure mode is: the person in the bathroom becomes
incapacitated or dies.

------
caiocaiocaio
Good article, but what they failed to notice was that the bathtub already
blocks both doors from opening.

~~~
lstamour
Okay, how would tying the two doors together prevent the doors from opening if
the doors opened inwards? It’s pretty obvious the doors would have to open
outwards from the bathroom into each suite. So the bathtub’s size and position
in any diagram is even more irrelevant, I’d suggest.

~~~
sjburt
It's a poor drawing. They look like doors that open inward. Doors that open
outward would be need to be set more deeply into the door frame.

~~~
handojin
A poor drawing and a worse excuse.

There's only one way this could work and how it's drawn has very little to do
with it.

------
aluminussoma
What if the high humidity of the bathroom causes the leather strap to break at
an inopportune time? What happens if the strap gets misplaced or stolen? This
is not a good idea.

~~~
3131s
> _What if the high humidity of the bathroom causes the leather strap to break
> at an inopportune time?_

I doubt that would happen, but use something other than leather?

> What happens if the strap gets misplaced or stolen?

Replace it?

------
whoisjuan
A designed degradation, also common in software. For instance, the low battery
mode in iOS is a designed degradation around the fact that is close to
impossible to improve the capacity of a lithium battery (the soloution would
be a completely new kind battery) so they allow people to disable non-critical
features to get a slower battery drain.

“Unlike common designs, excellent designs can circumvent the existence of
“unhappy” conditions as well as the influence of other low-performance
designs. Many times this requires the new design to lower its own performance
and although this is not ideal, this is usually a trade-off that can help to
maximize the existing conditions.”: [https://uxdesign.cc/designed-
degradations-ux-patterns-for-ho...](https://uxdesign.cc/designed-degradations-
ux-patterns-for-hostile-environments-7f308d819e50)

~~~
drusepth
In what way is the design of the room a degradation? As I understand it, the
hooks work as well as (if not better than) the locks you'd otherwise have.

~~~
whoisjuan
The degradation is the string that keeps both doors shut. It degrades the
experience of the bathroom because it limits mobility inside of it but this
degradation was designed to circumvent a larger deficiency of the design
(shared bathrooms).

~~~
chii
The hooks could double up as towel racks. And also, if the doors are near to
the edge of the wall, the hooks will be near the wall too, and so not really
take up space.

And it's not like you'll be dancing in the bathroom, so it taking up some room
that otherwise won't really be used isn't as big a problem as privacy.

------
hgdsraj
No need for a strap, Bluetooth linked locks that are automated so when one
opens the other does to. Or put the lock on the wall rather than on the door
and have a mechanical device running up and through the roof to the other
door, configured such that the two door locks are restricted similar to the
automation.

~~~
tom_
But why the need for Bluetooth, when you have a strap?

~~~
whatsstolat
I'd know what I'd bet on to actually work.

