Help me optimize my elevator travel
September 17, 2013 12:04 PM Subscribe
I work in a building with two elevator banks, six cars per bank. One covers floors 2 - 20. The other covers floors 20 - 38. Both, obviously go to the lobby. My office is on floor 20, so my co-workers and have our choice of which elevator bank to choose from for our trips up and down.
Almost since the day we moved in, most people in the office seem to show a preference for the 20 - 38 bank, presumably because there is no interruption for other floors on either the trip up from, or the trip down to, the lobby. Lately, though, I've been beginning to wonder if this is really is the fastest way up or down.
If one presumes relatively equal populations on all floors, uniform arrival and departure rates of workers in the building, and equal numbers of elevators in each bank, how would you model this situation to decide, over a large number of trips, whether one bank is really faster for us or not?
Almost since the day we moved in, most people in the office seem to show a preference for the 20 - 38 bank, presumably because there is no interruption for other floors on either the trip up from, or the trip down to, the lobby. Lately, though, I've been beginning to wonder if this is really is the fastest way up or down.
If one presumes relatively equal populations on all floors, uniform arrival and departure rates of workers in the building, and equal numbers of elevators in each bank, how would you model this situation to decide, over a large number of trips, whether one bank is really faster for us or not?
how would you model this situation to decide, over a large number of trips, whether one bank is really faster for us or not?
I would ask the building foreman.
posted by Tanizaki at 12:07 PM on September 17, 2013 [1 favorite]
I would ask the building foreman.
posted by Tanizaki at 12:07 PM on September 17, 2013 [1 favorite]
You could make a basic argument that every floor will have a roughly equal number of trips to and from the lobby so there is no advantage in picking elevators to a specific set of floors. So then the only variable is how many stops on the way. You can't do better than 0 so you should go with the 20-38 group.
posted by crocomancer at 12:11 PM on September 17, 2013 [7 favorites]
posted by crocomancer at 12:11 PM on September 17, 2013 [7 favorites]
Almost since the day we moved in, most people in the office seem to show a preference for the 20 - 38 bank, presumably because there is no interruption for other floors on either the trip up from, or the trip down to, the lobby. Lately, though, I've been beginning to wonder if this is really is the fastest way up or down.
How could it possibly fail to be the fastest way? That elevator is going directly from your floor to the lobby with zero stops. The other elevator will always make between zero and 18 stops. It can't be FASTER than the favored elevator.
posted by showbiz_liz at 12:13 PM on September 17, 2013 [13 favorites]
How could it possibly fail to be the fastest way? That elevator is going directly from your floor to the lobby with zero stops. The other elevator will always make between zero and 18 stops. It can't be FASTER than the favored elevator.
posted by showbiz_liz at 12:13 PM on September 17, 2013 [13 favorites]
I don't think there's enough information here to model this. Things like - how many workers can each elevator hold? How many workers in each arrival/departure rush hour? Do you want to account for, on the way down especially, people calling and stopping the elevator prior to your stop? How many are doing that? What is the speed of the elevators (this does actually matter - see below). I agree that a large-scale empirical study would be best. Recruit some coworkers.
How could it possibly fail to be the fastest way? That elevator is going directly from your floor to the lobby with zero stops. The other elevator will always make between zero and 18 stops. It can't be FASTER than the favored elevator.
I had the same thought, but the wait for the 20-38 elevators might be longer than the wait for the 2-20 elevators, sufficient to make up for the difference. I am highly skeptical that it would be true (they would have to be incredibly slow elevators, such that the travel time is way more than the time needed to stop, discharge, and restart), but it's possible.
posted by muddgirl at 12:16 PM on September 17, 2013 [1 favorite]
How could it possibly fail to be the fastest way? That elevator is going directly from your floor to the lobby with zero stops. The other elevator will always make between zero and 18 stops. It can't be FASTER than the favored elevator.
I had the same thought, but the wait for the 20-38 elevators might be longer than the wait for the 2-20 elevators, sufficient to make up for the difference. I am highly skeptical that it would be true (they would have to be incredibly slow elevators, such that the travel time is way more than the time needed to stop, discharge, and restart), but it's possible.
posted by muddgirl at 12:16 PM on September 17, 2013 [1 favorite]
Because you have a guaranteed "express" run in the 20-38 group, the only possible way that the 2-20 group could do better is if the 20-38 elevator took longer getting to you when you called for it. And that delay would have to be longer than all of the stops that the 2-20 elevator would make.
That could be easily enough tested by pressing the call button on each elevator bank and timing the arrival of an elevator. Average out the response times over your preferred sample size and see if there's a difference.
posted by AgentRocket at 12:17 PM on September 17, 2013 [3 favorites]
That could be easily enough tested by pressing the call button on each elevator bank and timing the arrival of an elevator. Average out the response times over your preferred sample size and see if there's a difference.
posted by AgentRocket at 12:17 PM on September 17, 2013 [3 favorites]
That could be easily enough tested by pressing the call button on each elevator bank and timing the arrival of an elevator. Average out the response times over your preferred sample size and see if there's a difference.
However, the wait time would be primarily affected by the current usage of other people in the building, so you'd have to do it at the time you'd be calling an elevator. And doing that at peak hour might be kind of a dick move, unless you actually have people waiting to get on each elevator.
posted by jacalata at 12:28 PM on September 17, 2013
However, the wait time would be primarily affected by the current usage of other people in the building, so you'd have to do it at the time you'd be calling an elevator. And doing that at peak hour might be kind of a dick move, unless you actually have people waiting to get on each elevator.
posted by jacalata at 12:28 PM on September 17, 2013
I'm thinking it's going to highly correlate with the number of employees on each floor. If there are 50% less employees on 20-38 than 1-20 then the express elevator should be quicker. If the numbers are roughly equal than I suspect the trip times will average out to roughly equal too.
posted by COD at 12:28 PM on September 17, 2013
posted by COD at 12:28 PM on September 17, 2013
Because you have a guaranteed "express" run in the 20-38 group, the only possible way that the 2-20 group could do better is if the 20-38 elevator took longer getting to you when you called for it. And that delay would have to be longer than all of the stops that the 2-20 elevator would make.
Just because of that, though, going down might be quicker in the 2-20 elevator than the 20-38. When you push the call button to go down, the 2-20 bank will come right to you with no stops as soon as it's available. For the 20-38 elevator, you'll have to wait for every stop it makes on the way down to you, but then you get a non-stop ride to the lobby. That seems like it would balance out though, assuming similar occupancy on all levels (because you'll have as many stops on the 2-20 elevator on your way to the lobby as the 20-38 elevator does on its way to the 20th floor).
The ride up seems like a no-brainer, but with one small wrinkle. Taking the 20-38 elevator means no stops guaranteed up to the 20th floor, so the only delay for it would be the time it takes to get to the lobby. Meanwhile, the 2-20 elevator will probably have some stops on the way up, but will also always be closer to the lobby, requiring less travel time to get there. So, if you're in the lobby watching, it may just seem like the 2-20 elevators are faster because they can complete more trips in the same amount of time than the 20-38 ones can.
If someone really wants to get into the math of it, which would be far too complex for me, the elevator type probably used in the building would be something like this (assuming a fairly new elevator), and you could probably safely assume a 12' story (although possibly significantly higher for the ground floor).
posted by LionIndex at 12:29 PM on September 17, 2013
Just because of that, though, going down might be quicker in the 2-20 elevator than the 20-38. When you push the call button to go down, the 2-20 bank will come right to you with no stops as soon as it's available. For the 20-38 elevator, you'll have to wait for every stop it makes on the way down to you, but then you get a non-stop ride to the lobby. That seems like it would balance out though, assuming similar occupancy on all levels (because you'll have as many stops on the 2-20 elevator on your way to the lobby as the 20-38 elevator does on its way to the 20th floor).
The ride up seems like a no-brainer, but with one small wrinkle. Taking the 20-38 elevator means no stops guaranteed up to the 20th floor, so the only delay for it would be the time it takes to get to the lobby. Meanwhile, the 2-20 elevator will probably have some stops on the way up, but will also always be closer to the lobby, requiring less travel time to get there. So, if you're in the lobby watching, it may just seem like the 2-20 elevators are faster because they can complete more trips in the same amount of time than the 20-38 ones can.
If someone really wants to get into the math of it, which would be far too complex for me, the elevator type probably used in the building would be something like this (assuming a fairly new elevator), and you could probably safely assume a 12' story (although possibly significantly higher for the ground floor).
posted by LionIndex at 12:29 PM on September 17, 2013
Elevator optimization is a pretty well studied problem, the floor 20 split is probably well thought out for the building size. The rest location of a given elevator may be determined very simply or may be 'smart' and depend on time of day and location of other elevators.
If the 1-20 bank are lightly used, it may be faster for an individual to hope in one and hit 20, especially if there is light traffic between floors. Again that may be time of day dependent. Unless there are long wait times the existing setup is probably as close to optimum as reasonable.
Walking up is probably the healthiest option. ; -)
posted by sammyo at 12:29 PM on September 17, 2013
If the 1-20 bank are lightly used, it may be faster for an individual to hope in one and hit 20, especially if there is light traffic between floors. Again that may be time of day dependent. Unless there are long wait times the existing setup is probably as close to optimum as reasonable.
Walking up is probably the healthiest option. ; -)
posted by sammyo at 12:29 PM on September 17, 2013
Response by poster: The only reason I've been thinking about this at all is that recently I've taken to using the lower bank out of curiousity and subjectively perceive that I've been getting cars a little faster than in the upper bank. Totally anecdotal and non-scientific, but it made me wonder if there was something going on I might not have been taking into account. Like perhaps if cars going up will only go down if they hit the top or there are no waiting calls above them.
posted by hwestiii at 12:29 PM on September 17, 2013
posted by hwestiii at 12:29 PM on September 17, 2013
Do any of the floors have less offices on them, like conference rooms instead? Where's the cafeteria?
posted by jwells at 12:49 PM on September 17, 2013 [1 favorite]
posted by jwells at 12:49 PM on September 17, 2013 [1 favorite]
When you push the call button to go down, the 2-20 bank will come right to you with no stops as soon as it's available.
I don't know if this is true if there is a lot of inter-floor movement as well. If an empty elevator is traveling up from the lobby to a call on the 20th floor, and I press the "UP" call button on, say, the 5th floor, the elevator would stop for me, no?
These sorts of uncertainties are why modeling would be difficult compared to just measuring trip times.
posted by muddgirl at 12:49 PM on September 17, 2013
I don't know if this is true if there is a lot of inter-floor movement as well. If an empty elevator is traveling up from the lobby to a call on the 20th floor, and I press the "UP" call button on, say, the 5th floor, the elevator would stop for me, no?
These sorts of uncertainties are why modeling would be difficult compared to just measuring trip times.
posted by muddgirl at 12:49 PM on September 17, 2013
Can you wait for both elevators at the same time or do you need to commit to a bank before you call the elevator? If it's the former (and you don't mind racking up negative karma) you should call both and get on whichever arrives first (also, note which one arrives first). The trip on the upper bank will always be faster (or equally fast) so the real variable here is wait time.
posted by telegraph at 12:55 PM on September 17, 2013
posted by telegraph at 12:55 PM on September 17, 2013
Elevators are programmable. For each, you can set:
- The speed the elevator travels
- The amount of time a door is open when it detects someone standing in the doorway
- The amount of time that passes after the doors close but before it starts moving and also after stopping but before the doors open
- Maybe most importantly for your question, which floor the elevator parks itself at when not being called.
Also, elevators work differently and have different motors which work at different powers and speeds.
Given all that, I'd ask the building maintenance department.
posted by Houstonian at 12:59 PM on September 17, 2013 [1 favorite]
- The speed the elevator travels
- The amount of time a door is open when it detects someone standing in the doorway
- The amount of time that passes after the doors close but before it starts moving and also after stopping but before the doors open
- Maybe most importantly for your question, which floor the elevator parks itself at when not being called.
Also, elevators work differently and have different motors which work at different powers and speeds.
Given all that, I'd ask the building maintenance department.
posted by Houstonian at 12:59 PM on September 17, 2013 [1 favorite]
I don't know if this is true if there is a lot of inter-floor movement as well. If an empty elevator is traveling up from the lobby to a call on the 20th floor, and I press the "UP" call button on, say, the 5th floor, the elevator would stop for me, no?
You're right, I didn't think of that. How much of a factor that is would depend on who occupies the different floors (like if one company has multiple levels or something). I'd guess the only other users doing that would be maintenance, and there's probably a separate service elevator, but they may use the main ones if they're more convenient.
posted by LionIndex at 12:59 PM on September 17, 2013
You're right, I didn't think of that. How much of a factor that is would depend on who occupies the different floors (like if one company has multiple levels or something). I'd guess the only other users doing that would be maintenance, and there's probably a separate service elevator, but they may use the main ones if they're more convenient.
posted by LionIndex at 12:59 PM on September 17, 2013
Is the 20-38 elevator often full when it gets to 20?
Are there stairs available? Some lower floor workers probably take the stairs, lowering the number of total employees on those floors (not sure if it would be enough to make a difference, though).
posted by troika at 12:59 PM on September 17, 2013
Are there stairs available? Some lower floor workers probably take the stairs, lowering the number of total employees on those floors (not sure if it would be enough to make a difference, though).
posted by troika at 12:59 PM on September 17, 2013
I am not sure why people are assuming that that the express (20-38 elevator) is going to have a faster run. If I am on level 20 and push the call button at at 12:00:00 and it takes let-us-say fifteen seconds to get there, what happens if someone on level 30 pushes the button at 12:00:10, and someone on level 35 pushes the button at 12:00:15? Obviously, I then go up before I go down.
Do the elevators have any indicator visible as to what floor they are on? It seems that if the express elevator were above you and descending, it would be faster on average than either one ascending.
posted by ricochet biscuit at 1:05 PM on September 17, 2013
Do the elevators have any indicator visible as to what floor they are on? It seems that if the express elevator were above you and descending, it would be faster on average than either one ascending.
posted by ricochet biscuit at 1:05 PM on September 17, 2013
recently I've taken to using the lower bank out of curiousity and subjectively perceive that I've been getting cars a little faster than in the upper bank.
It wouldn't be surprising that the wait time for a car would be less for the cars in the lower bank; each bank serves 19 floors other than the lobby, so if all floors have similar populations with similar work schedules and similar elevator habits, the time spent on floors 2-20 for the lower bank would be similar to the time spent on floors 20-38 for the upper bank. The additional time to go from 1-20 for the upper bank would mean longer overall trips for those cars, leading to a slightly longer wait time.
However, it's highly unlikely that the longer wait time for the upper bank would be enough to offset the quicker travel time once you're in the car, as you have the guaranteed next stop when using the upper bank. But as muddgirl notes, it can't be strictly ruled out without empirical study.
posted by DevilsAdvocate at 1:05 PM on September 17, 2013
It wouldn't be surprising that the wait time for a car would be less for the cars in the lower bank; each bank serves 19 floors other than the lobby, so if all floors have similar populations with similar work schedules and similar elevator habits, the time spent on floors 2-20 for the lower bank would be similar to the time spent on floors 20-38 for the upper bank. The additional time to go from 1-20 for the upper bank would mean longer overall trips for those cars, leading to a slightly longer wait time.
However, it's highly unlikely that the longer wait time for the upper bank would be enough to offset the quicker travel time once you're in the car, as you have the guaranteed next stop when using the upper bank. But as muddgirl notes, it can't be strictly ruled out without empirical study.
posted by DevilsAdvocate at 1:05 PM on September 17, 2013
The upper floors are more exclusive and probably more expensive than the lower floors. It follows that they will have fewer workers per square foot. In addition, management is likely to be more responsive to the needs of the upper-floor tenants, and so those elevators will be in better working order. They may have additional benefits, such as doors that operate more quietly or more quickly.
In addition, by riding the express elevators you will be congregating with more desirable elevator companions both during your wait and during your ride.
For all these reasons, if you are not willing to measure you should ride the express elevator.
posted by alms at 1:25 PM on September 17, 2013
In addition, by riding the express elevators you will be congregating with more desirable elevator companions both during your wait and during your ride.
For all these reasons, if you are not willing to measure you should ride the express elevator.
posted by alms at 1:25 PM on September 17, 2013
Obviously, I then go up before I go down.
I'm confused. If you get on an elevator that indicates it's a down elevator, then you're going down. The elevator isn't going to go back up to pick up higher floors before going down. That's one reason why there are three elevators in each bank.
posted by muddgirl at 1:32 PM on September 17, 2013 [2 favorites]
I'm confused. If you get on an elevator that indicates it's a down elevator, then you're going down. The elevator isn't going to go back up to pick up higher floors before going down. That's one reason why there are three elevators in each bank.
posted by muddgirl at 1:32 PM on September 17, 2013 [2 favorites]
I can't help wondering why the 2 options are 2 - 20 and 20 - 38, rather than 2 - 19 and 20 - 38. Or 2 - 20 and 21 - 38.
posted by still_wears_a_hat at 1:36 PM on September 17, 2013
posted by still_wears_a_hat at 1:36 PM on September 17, 2013
I can't help wondering why the 2 options are 2 - 20 and 20 - 38, rather than 2 - 19 and 20 - 38. Or 2 - 20 and 21 - 38.
If you're on floor 15 and you need to go to floor 35, it's more convenient not to go down then up.
posted by jeather at 1:40 PM on September 17, 2013 [2 favorites]
If you're on floor 15 and you need to go to floor 35, it's more convenient not to go down then up.
posted by jeather at 1:40 PM on September 17, 2013 [2 favorites]
If it were me, I'd get a friend in my 20th floor office to agree to ride the elevators with me for a week or so and we'd "race". Both people press their buttons at the same time, and record who gets there first. Then see who wins the most over the course of the week.
posted by Weeping_angel at 1:41 PM on September 17, 2013 [2 favorites]
posted by Weeping_angel at 1:41 PM on September 17, 2013 [2 favorites]
The computer that runs the elevators might be logging this data, can you get access to the log files?
posted by Confess, Fletch at 1:51 PM on September 17, 2013
posted by Confess, Fletch at 1:51 PM on September 17, 2013
Fewer people might use the 2-20 elevators, because it is more feasible to walk for the first few floors.
posted by freezer cake at 4:23 PM on September 17, 2013
posted by freezer cake at 4:23 PM on September 17, 2013
The 1 - 20 elevator will only have to come from floors 1 - 20, and will use a bit less electricity, so that's what I'd use. Or I'd get in shape by walking up the stairs, or taking the elevator to 15, and walking from there, gradually increasing. I was in better shape when I worked on the 8th floor.
posted by theora55 at 4:42 PM on September 17, 2013
posted by theora55 at 4:42 PM on September 17, 2013
I don't have an answer, but I would also consider the possibility that it may make sense to take one bank up and the other bank down.
posted by JohnnyGunn at 5:53 PM on September 17, 2013
posted by JohnnyGunn at 5:53 PM on September 17, 2013
Upper floors are often penthouse-like and can have lower person density. Lower floors often contain things like meeting rooms, etc. Or maybe you have a law firm on 28 that is crammed in like sardines and 12-18 are currently sitting empty.
Is there a 13th floor? I'm still amazed how many modern buildings don't have one. That would mean one less floor serviced by 1-20.
There's really no way to figure this out without actually testing it. I would expect it's pretty close, though the answer could change depending on the time of day. (Maybe everyone on the upper floors works late so the elevators are quick at quitting time, etc.)
A stopwatch timing from pushing the call button to the doors opening on your floor will give you the answers you need. For better science get a co-worker to time as well. One of you takes 1-20 for a week, the other 20-38 for a week.
Keep in mind that if your results come up with one side being clearly the best, telling everyone about it could result in more people taking that set of elevators, thus slowing down service in that stack.
posted by Ookseer at 6:24 PM on September 17, 2013
Is there a 13th floor? I'm still amazed how many modern buildings don't have one. That would mean one less floor serviced by 1-20.
There's really no way to figure this out without actually testing it. I would expect it's pretty close, though the answer could change depending on the time of day. (Maybe everyone on the upper floors works late so the elevators are quick at quitting time, etc.)
A stopwatch timing from pushing the call button to the doors opening on your floor will give you the answers you need. For better science get a co-worker to time as well. One of you takes 1-20 for a week, the other 20-38 for a week.
Keep in mind that if your results come up with one side being clearly the best, telling everyone about it could result in more people taking that set of elevators, thus slowing down service in that stack.
posted by Ookseer at 6:24 PM on September 17, 2013
Without an extensive amount of additional information, jeffjon has the best (and first!) answer: you need to measure something. Every "theory" of how to optimize elevator travel time will be completely useless in the face of all the potentially unknown considerations, and the only thing to do is perform a series of experiments to determine the correct answer empirically.
posted by grog at 6:29 PM on September 17, 2013
posted by grog at 6:29 PM on September 17, 2013
I worked as a courier in a downtown market. As time was at a premium for me, I've measured this.
Take 20-38. It's direct. 2-20 doubles your waiting time.
posted by converge at 1:55 AM on September 18, 2013
Take 20-38. It's direct. 2-20 doubles your waiting time.
posted by converge at 1:55 AM on September 18, 2013
« Older Any ideas for a scavenger hunt prize? | Can I use Mainstage 3 instruments in Garageband... Newer »
This thread is closed to new comments.
posted by jeffjon at 12:07 PM on September 17, 2013 [8 favorites]