Queue Theory and Design

Roman Mars (RM): This is 99% Invisible. I’m Roman Mars.
RM: In the US, they’re called lines. In Canada, apparently they’re called line-ups sometimes.
Benjamen Walker (BW): And I was once interviewed live on Canadian National Radio and they started talking about line-ups and we had a conversation about police for five minutes until I realized what they were talking about.
RM: Pretty much everywhere else, it’s known as a queue.
BW: I like “queue” the best.
RM: Yeah, me too.
RM: That’s Benjamen Walker. He’s obsessed with queues. He keeps sending me emails with links to YouTube videos of queues.
BW: You have psychology students filming their surreptitious queue experiments, you have asian roadrage videos, you’ve got people filming fights that break out in queues.
“Unless you’re gonna physically move me, nothing’s gonna happen! So understand that I’m not getting out of this line. Understand that none of you are going to stop me from being in this line.”
BW: I like to call YouTube the queue-hole. And when I found this lecture by “Dr. Queue,” I immediately made an appointment to go and see him.
Richard Larson (RL): I’m Dick Larson. I’m a professor at MIT. And I guess my nickname is Dr. Queue.
BW: Dick Larson is a queue theorist.
RL : Just about every day we experience queuing in some aspect of our lives.
BW: Dick Larson studies the mathematical and psychological models of queuing systems.
RL: Unfortunately, often times too many queues on a day to day basis.
BW: Dr. Queue is able to put his professional knowledge to work everywhere he goes.
RL: I have my own ways through supermarkets, but particularly if you have to go to the deli counter and get a number? You RUN to the deli counter as soon as you go to the super market and get your number and the you start walking around and doing your regular shopping and you watch the numbers drop down. And as soon as it gets close to yours, then you go back. So that’s a queue that’s been avoided because it’s a queue within a queue. So I have little ideas like this.
BW: Dr. Queue hates waiting in line as much as you and I do. But he does respect the well-designed queue.
RL: The Machievellian experts of queue design are people are Disney World and the Disney properties. They mastered the idea that people can be happy waiting forty minutes in line for a four minute ride. I think it’s fantastic.
BW: Disney is very serious about queue design.
RL: They employ about eighteen or so operations researchers. They call them “Imagineers”
BW: These imagineers have mastered the golden rules of queue design.
RM: The first is to keep your customers entertained while they wait in line.
RL: Their guests think that the amusement has started before they actually sit in the ride.
RM: They’ll have video screens along the queue route with games. And if the lines are getting really ugly? A park manager will send in a sweaty man in a full body costume.
RL: And so they’re entertained and their amused while they’re waiting in line.
RM: The second rule. Manage expectations.
RL: Always manage your expectations such that you’ll deliver above the performance you say. For instance, if the line says you can anticipate a 45 minute wait if the line is out to this point, really it might be only 35 minutes. So therefore, if you look at your watch and in 35 minutes you’re getting on the line and the dad and the mom and the two kids say “Hey! We’re ten minutes ahead of schedule!” So that’s great. You’ve waited 35 minutes and you say “we just save ten minutes because we thought we were going to have to wait for 45 minutes.”
BW: Queue theory is about a hundred years old now. But it wasn’t until the 1950s that the profession really came into its own.
RL: After World War II there was a burst of economic activity, a lot more high rise buildings, high rise hotels and offices, and all of a sudden owners of these buildings were getting complaints about rush hour delays for elevators. In those days, of course, they didn’t have microprocessors to optimize the movement of the elevators. Many of the elevators actually had humans as operators, as pilots, so to speak. So Russ Ackoff, who was professor at University of Pennsylvania sent one of his research aids to New York City to check out these complaints about elevator delays. And indeed he found out that there were rush hours for elevators.
RM: Like 8 to 9 in the morning or 5 to 6 at night. Just like rush hour for cars.
RL: And so he said hmm. The traditional engineering approach- dynamite this building and start over again with twice as many elevator shafts because you’ve got more demand than you have capacity in these rush hours.
RM: In my experience, engineers are a lot more crafty than that, but let’s just go with it.
RL: But then, in a stroke of genius, he said maybe the problem is framed the wrong way. Maybe the problem isn’t the 90 seconds of wait for the elevators. Maybe the problem is the complaints about the 90 second waits for the elevators and if we could reduce the complaints substantially, maybe we’ll solve the problem. And then in another stroke of genius, he said well what if you give somebody a distraction, a diversion. Let’s try floor-to-ceiling mirrors next to all the elevators in an experimental building. So he got the money, put the mirrors in, watched for a month, and guess what? The complaints dropped to near zero. Men who were wearing ties could adjust their ties. Women could make sure their hair was organized ok.
RM: Or vice versa.
RL: Sometimes men and women were seen to flirt occasionally through the reflection. I guess it’s less provocative than eye-to-eye contact. The complaints dropped to near zero, problem solved. The statistics of the delay, unchanged. Ingenious.
RM: Mirrors won’t work at McDonald’s or a Whole Foods though. Many fast food restaurants and most grocery stores use parallel queues, where there’s a bunch of open lanes and you’re forced to pick one and stick with it. The one next to you could be going fast for any number of reasons and it’s totally frustrating, but you stay in your line. And you play the hand you’re dealt.
BW: But there’s another way to do it. A single serpentine line that feeds all of the open registers. It’s first-come-first-serve. It’s a queue designed for equality and fairness. And when there’s one line, both blantant and inadvertant queue-jumping is minimized.
RL: We call them slips and skips.
BW: And American companies, they used to pride themselves on designing these more egalitarian queues.
RL: Wendy’s is very proud that they’re the first ones in fast food that had the single serpentine line. American Airlines is very proud. They claim that they were the first ones to have a single serpentine line in airports, although British Air argues with them. They said they got it at the same time. There used to be a bank in New York called Chemical Bank and they used to claim that they were the first ones to have that in their bank lobbies. So there’s a certain pride to getting rid of inadvertant line-jumping by slips and skips by having the single serpentine line.
BW: But today, queue design is changing. More and more we’re encountering queues that are designed so that different levels of service can be provided to different groups of people.
RL: Priority queues and giving certain people piorities over others, you could see it in amusements, like Disney, but more seriously, it occurs in some life and death situations. Like queuing for organ donation transplants.
BW: My hypothesis is that this design change is connected to the queue rage that’s becoming more and more commonplace and available to watch for free on youtube. And I also believe that understanding this new queue theory will better help us understand the inequality and disparity that’s on the rise in this country.
RL: Yeah, you might say, well why should somebody with a lot of frequent flier milage get automatically bumped up to first class- as I found out I recently was- on some flights? And therefore can escape the TSA queue in airports. And I feel a little bit guilty about that. Just yesterday I did this twice. And I felt a little bit guilty because there are like thirty people in line and I went right to the front of it. And I thought hmm. Why is this fair? Just because I fly a little bit more than the others do? And so I think your question is a deep one and requires some more thought and discussion.
RM: 99% Invisbile was produced this week by Benjamen Walker and me, Roman Mars. Do I need to tell you about Benjamen Walker again? Too Much Information from WFMU? Understand, it will make your life better. This is a project of KALW, local public radio in San Francisco and the American Instiute of Architects in San Francisco.

Comments (3)


  1. I am very curious about the Japanese song at the end of the episode– part of my brain wanted me to think that it was a Japanese children’s choir cover of Peter Bjorn and John’s “Young Ones” but I wasn’t sure… I had subscribed to your excellent podcast months ago but it was only a bout of insomnia opening up two nights of hours that I did a huge “listening binge” and now I am a soon-to-donate minion. “Kowloon Walled City”… man o man… Anyway, I am going to Cambodia this summer for another round of fieldwork (I am a PhD archaeology sutdent at UIC)– there’s a lot of cool architecture stories over there but one is the legacy of the still-living (the Khmer Rouge regime only fell in ’79!) master of New Khmer Architecture, Vann Molyvann http://en.wikipedia.org/wiki/Vann_Molyvann His Bassac Theater just burned down last month and it was treated as a huge tragedy (a lot of Cambodia’s glory is derived from architecture- from the famed Angkor Wat to earlier constructions that they are trying to market in order to decrease destrcutive pressure of 4 millions annual visitors [2 mil foreign]), and one of his artist’s colonies on the riverside is now a sort of far sunnier little version of an involuted lawless Kowloon Walled City… Anyway, thanks for doing the show, maybe you know the name of the Japanese song, and maybe you will also be interested in a Cambodian-flavored collabo at some point- I will be there all summer. Thanks! Keep ’em coming!

    Sincerely, Jacob

    PS- Thank you for putting my city’s wonderful Chicago accents (born and raised with one) on the air during the Trading Places episode

  2. I.T

    I’d recently moved from the United States to my home country of Nigeria where queueing is a relatively recent practice: most places, especially banks, still get it wrong. I was in one of 2 lines -the american in me isn’t in love with the word ‘queue’- being served by 3 tellers. My line was directly in front of 1 teller, the other line to the right of me was in front of another teller and the third teller was off to the far right. So naturally those 2 tellers ended up serving that line while my line was almost exclusively being served by the 1 teller.
    When I was in the front of my line, a lady 2 of 3 spots in line behind me started agitating about the other line moving faster and insisting that I should go to one of the 2 right tellers when the next person was called. When I didn’t respond to her and someone from the right line went up next, she pushed to the front of the line. I told her off roundly, and told her to get back to her place in line because her time was not any more important than everyone else in line ahead of her.
    She was obviously very surprised, I think by 2 things: that, being younger, I spoke that sharply to her (that’s a societal no-no in Nigeria), and by my foreign accent. She looked at me for a second and then said in a sing song mocking tone: “ms. London, ms. America”
    I came away from that encounter with a few things: here people generally do not have the sense of ownership to their place in line like I do, because so-called “VIPs” always get fast-tracked, also due to cultural norms older people also cut in and are excused, and -like in my encounter- anyone who’s loud enough or strong enough or assertive enough tries to do what that lady wanted to, and just cut in front of everyone and ‘everyone’ doesn’t want to make a fuss so stand in line quietly and let’s her go ahead.
    …so there’s my story about queue theory. It’s a great show and I’m quite a fan -I.T

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