Wednesday, May 23, 2012

Queues in the News

You might not have noticed, but queues have been in the news a lot lately. Not from the standpoint of computer performance but people performance or more accurately, crowd control. Most recently, queues popped up in the context of long delays expected at Heathrow airport due to big crowd arrivals for the London Olympics.

In a queue, at least everyone is pointing in the same logical direction. Moreover, if you snake the queue, as they do at Disneyland, people always feel close to the destination and can see it getting even closer as customers ahead of them are processed. That helps to minimize their level of frustration: the control part. For some reason, the post office hasn't figured this out yet.

And, last but not least, queues and computer performance still remain an inevitable perennial. Most recently having to do with the Internet.


  1. @pjpuglia tweeted about a lack of empirical waiting times in hospitals. Waiting-time measurements (as in, collecting actual data) seem to be subpar in that industry, especially when it comes to patients with different levels of medical urgency. Ironically, if you crack open any queueing theory textbook, you'll find that most of the theoretical discussion centers around the analysis of waiting-time distributions.
  2. Maybe Urgy Queue can help. (Translated from the SF description) Avoid endless waits in the ER. "Urgy Queue" is an application designed for mobile devices that will be used to estimate the waiting time in the emergency department of each hospital, so that the consultation, the user can decide which hospital to go to wait for the shortest possible time. The performance and usability of the application is fairly simple, since all you have to do the user will select a color for the hospital where you are. This color will go from red (high hopes) to Green (low standby). The central server will collect the information that users have been recorded and displayed in the interface of the mobile enabled devices ordered in different ways: hospital ± nearby hospital with more or less than the expected waiting time. The information on the status of each hospital is updated in real time.
  3. Waiting for a bus? It's common knowledge that bus arrivals tend to bunch up and come in threes. But there are no reliable measurements for buses, either. So, Georgia Tech actually came up with a novel idea: doing controlled experiments using GPS. The results of their analysis were reported on a CNN web site that even included some of the mathematical equations. Gasp! Using Markov Chain theory—a type of state transition technique used in every queueing theory textbook—they came up with an anti-bunching formula. The space between buses is called the "headway" and the analysis shows how the headway changes over time. In the beginning, each bus starts out with its own distinct headway. Under the new scheduling algorithm, the buses adaptively stabilize around a common headway value which acts like a spring keeping the buses separated.
I'll have more to say about all these things in the upcoming GDAT class during the week of June 11-15.