
The Elevator Button Problem - jgrahamc
http://blog.jgc.org/2010/06/elevator-button-problem.html
======
Avernar
> There's nothing to stop you contradicting yourself by indicating a different
> direction of travel. Which makes you wonder why you had to indicate the
> direction in the first place.

You had to indicate the direction in the first place because the system can
give you a cab that's already going in that direction. Even if nobody is in
the cab it may be going to another floor that someone has pressed the call
button before you. If you press a button for the opposite direction it will
still go in it's original direction.

Eventually it will change direction and go your way but that just ensures
you'll spend the maximum time in the elevator. During your ride in the wrong
direction another cab may have freed up or there could have been one already
free but a few floors further than the one going in the other direction.

That's also why elevators have the up and down lit arrows at the top of the
door to indicate which way it's going. This keeps you from getting on one
going the wrong way if it come to your floor first to either drop off or if
both call buttons were pressed.

------
_nalply
There's another way. Indicate which floor you want to get on. No buttons
inside the elevator. Works fine for not too many floors. I know a mall with
four floors where this is implemented. 2 underground parking levels, 1 ground
floor and a floor above it for the gym and spa at the top.

~~~
mshook
That's how elevators work in the company I am at. You don't have an up or down
button. Just a keypad with all the floors (and some additional buttons for
people with disabilities).

The way it works:

\- when you select a floor number, a LCD screen tells you which elevator of
the pool you'll be using

\- in the elevator, no buttons except alarm, keep doors open, close doors

\- in the elevator, there's a display that tells you on which floors the
elevator will stop (because you can't have the whole "floor button is lit up")

The good things about this system:

\- you don't get to be in an elevator which is going to stop on all floors
because the system is intelligent enough to allocate elevators appropriately

\- better use of the resources (eg you don't have everyone getting in the
first available elevator, going up and then a second one comes and is empty)

\- no more pranking anyone by pushing all the buttons (because you can only do
that while waiting for one and the system will dispatch the demanded floors to
the pool)

The bad:

\- you can't change your mind once you called it. If you selected a floor,
even if you don't get in the elevator, it'll stop there

\- you can't change your mind once you're in. Best case is you can stop at an
intermediate floor if someone is going there or called the elevator.

\- it's frustrating when the system allocates an elevator for you and it comes
after one that isn't going anywhere.

~~~
Avernar
> no more pranking anyone by pushing all the buttons (because you can only do
> that while waiting for one and the system will dispatch the demanded floors
> to the pool)

While it would stop pranking it opens it up to denial of service. Most new
elevators don't let you select more floors than the persoson capacity of the
cab. With the external keypad system someone could hide on a floor with nobody
around and keep entering floor numbers.

Incidentslly, I was on a full elevator when a kid pressed all the buttons and
ran out (this was before the protection I mentioned became popular). I could
hear the groans of my fellow passengers. Fortunately I was shown a trick by an
elevator tech for that brand a few weeks ago. I held the door open and reached
up and tripped the door switch. All the lit buttons went out and I just
aelected my floor again. Got a round of thank yous as everyone else selected
their floor again.

> you can't change your mind once you're in. Best case is you can stop at an
> intermediate floor if someone is going there or called the elevator.

That could be rage inducing. Imagine forgetting something in your car and
being stuck going up to the top of a very tall building. And then going all
the way back down.

There really should be a button for "let me off at the next valid floor". I'd
hate to be stuck in an elevator when someone gets sick and has to hurl or
worse shit their pants.

