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A single line to 3 cashiers is ~3x faster than a separate line for each cashier

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Re: A single line to 3 cashiers is ~3x faster than a separate line for each cashier

#21

Post by JonnieCache »

digitalsushi wrote: post #11

I was at a Home Depot this summer in the garden section, 2 checkouts. I was straddling the middle, waiting for the next open lane. Some lady starts bumping into me with a large cart, pushing her way up my right. I looked at her with a frown, and she told me to pick a line. I told her I was 'next' and she scoffed and went into the right lane, and was serviced more quickly (but only randomly) These little mental models…

The clever answer is to stop worrying about the loss/gain of an insignificant couple of minutes and to use the time for introspection, problem solving, daydreaming, or whatever else it is you like to do in the comfort of your own skull. Although, for many here, that probably includes "worrying about queueing theory" so maybe my point is moot.

Re: A single line to 3 cashiers is ~3x faster than a separate line for each cashier

#22

Post by tgrass »

digitalsushi wrote: post #11

I was at a Home Depot this summer in the garden section, 2 checkouts. I was straddling the middle, waiting for the next open lane. Some lady starts bumping into me with a large cart, pushing her way up my right. I looked at her with a frown, and she told me to pick a line. I told her I was 'next' and she scoffed and went into the right lane, and was serviced more quickly (but only randomly) These little mental models…

I would agree with you even if I came up in line behind you.

But I would fully expect the majority to find fault in it. And reasonably so. The system is in place and it is multiple queues. The consequence of bucking the system is, at its most polite, a sneer and a scoff.

Leading left hand turns at a vehicular intersection may be the wiser alternative, but to flout a trailing left hand turn and jump through at the green is dangerous, rude and illegal.

Re: A single line to 3 cashiers is ~3x faster than a separate line for each cashier

#25

Post by jff »

smackfu wrote: post #18
nlawalker wrote: post #9

Most of the grocery stores in my area have installed self-checkout systems that are especially great if you just have a handful of items that all have UPCs (no produce or bagged bulk), don't have any items requiring an age check and possess at least the intelligence of a fifth grader. I mention this not just because it's relevant to the idea of waiting in line at a store, but because in every store where I've seen th…

Around here, the grocery self-checkout works the same as the normal checkouts, mainly because they just replaced the normal ones in place. (Also, self-checkouts suck. I bet their throughput is terrible compared to manned checkout lines. That teenage checkout girl is WAY better than I am at scanning stuff.)

Ah, but you see, anyone who writes checks (hellooooo, slowdown!) and anyone who is scared of technology (I think the two groups overlap a lot) will go wait in another line. So at least at my store, the self-checkout lanes have a lot of young people buying one or two items and paying with credit cards, which works out to a pretty good speed. Occasionally you get somebody who sits and stares at each screen of instructions for a good 30 seconds, but in general it moves well.

Re: A single line to 3 cashiers is ~3x faster than a separate line for each cashier

#26

Post by jff »

JoshTriplett wrote: post #12

It becomes even more obvious if you think of it like scheduling processes on a CPU. Why needlessly set CPU affinity and only run on a single CPU when you could just take the next available timeslice on any CPU?

Except there are reasons for CPU affinity, such as the cache.

Re: A single line to 3 cashiers is ~3x faster than a separate line for each cashier

#27

Post by pnathan »

FYI: This is an example of the branch of mathematics called queueing theory.

http://en.wikipedia.org/wiki/Queueing_theory

It's a fascinating study requiring a good knowledge of probability to use beyond the simplified models. It turns out from the math that throughput using a single queue is better than using multiple queues.

Re: A single line to 3 cashiers is ~3x faster than a separate line for each cashier

#28

Post by smackfu »

What I didn't see in this article is why retailers don't do this today. I see a lot of positives listed and no negatives, so it seems like a no-brainer, right? Yet the biggest retailers like Walmart and Target have tons of lanes, and even do staggered front/back lanes which are terrible for the customers. Is it because there are negative feelings to seeing a long line, and that people do not expect it to be fast so they abandon their purchase?

Re: A single line to 3 cashiers is ~3x faster than a separate line for each cashier

#29

Post by trustfundbaby »

It also has an engineering analogy in Apache Passenger Global queuing. And this article explains why it works the way it does http://blog.phusion.nl/2008/10/29/phusion-passenger-now-with...

As an aside: The Fry's Electronics store in my city does this and the line does move at a pretty brisk pace, but I had always thought it a rather odd setup till I read this and made the connection to global queuing in Passenger. fascinating.

Re: A single line to 3 cashiers is ~3x faster than a separate line for each cashier

#30

Post by jff »

robflynn wrote: post #14
blakehill wrote: post #2

So at least there's one thing that most big banks get right.

I first encountered this in non-banks at Fry's Electronics over a decade ago. It struck me as odd initially, but I quickly realized how much more efficient it was and began to prefer it -- especially when I ended up stuck behind a 10 minute checkout in which the person insisted on paying with a cheque.

It's really important at Fry's, when often as not you just get an empty box or a piece of paper saying "Give this man a monitor" and they have to send somebody out across the store to actually pick up your item. Or when you bring out your government purchasing card and they don't believe it's real, so you have to stand there for an hour while they try and figure it out (true story).
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