Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

online.wsj.com

Post reply on HN
Print view View original

11–20 of 172 posts

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

#11

Post by digitalsushi »

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 of efficiency always make the nervous introvert in me worry that I am wrong, or if society in general publishes people who try something different.

The naive answer is to avoid retail interactions.

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

#13

Post by aplusbi »

gdilla wrote: post #7
DTanner wrote: post #6

Earlier quoted context omitted.

Chapters also does this (here in Canada anyway).

The Wholefoods in NYC at TimeWarner does this. While Wholefoods in California doesn't.

All the wholefoods in NYC (that I've been to anyway) have done this. You know the voice that tells you which register to go to? That guy used to work (maybe still does?) at the one on 7th and 24th, and his job was to direct people to check outs.

He was replaced with an LCD screen and a speaker.

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

#14

Post by robflynn »

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.

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

#15

Post by jessriedel »

smackfu wrote: post #8

Wouldn't it be 3x the velocity, but the line is 3x longer, so your total wait time is the same? The article is mainly saying that people like moving faster, but is that really a phenomenon?

Yes. The bottleneck is the total throughput of the cashiers. Now, better deployment of cashiers can help. If you have N people come into your store, you're going to have to check them all out at some point. The problem is that if you always have enough cashiers to help people as soon as they are ready, you'll be paying cashiers to stand around during lulls. Stores try to avoid this by moving cashiers to other jobs when there's a lull, but this only helps for fluctuations with timescales long compared to the time it takes to start and finish a job.

hrabago's point is important, but it certainly doesn't justify the linkbait title. A single line will decrease the variance of the wait time. Since the customer's impression of the wait time is very non-linear, this might significantly reduce customer unhappiness. But that isn't some brilliant insight into the process of handling customers faster.

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

#17

Post by kenjackson »

hrabago wrote: post #10
smackfu wrote: post #8

Wouldn't it be 3x the velocity, but the line is 3x longer, so your total wait time is the same? The article is mainly saying that people like moving faster, but is that really a phenomenon?

No, because the cashiers handling smaller transactions finish quicker and can process more people. If you're stuck behind a guy which takes 2 minutes to check out, people in other lanes will be in their cars before you even begin checking out.

Here's a concrete example to make harabago's point clearer (since I think it is a little tricky). Imagine 9 people in line. Each person takes 1m to checkout except the first guy takes 10m. With three lines it looks like this (these are their wait times before being serviced):

   0   0   0  (first person in each line has no wait time)
   10  1   1
   11  2   2
If you sum up the total wait times you get: 27m

Now do this with a single file line with three cashiers:

   0   (first three people have no wait time)
   0
   0
   1   (only two people get processed at a time now)
   1
   2
   2
   3
   3
What you see is that one guy basically blocked one of the cashiers for the whole time, but the other two cashiers could continue to process. The total wait time: 12m

Change the numbers and you can create different factors for which the single file line is more efficient.

EDIT: Made a typo the first time on the wait times for the 3-line scenario. The wait time is actually 27m, not 25m.

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

#18

Post by smackfu »

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.)

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

#19

Post by neutronicus »

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.)

As much better as the teenage checkout girl is than I am at scanning, it's nothing compared to how much better she is at pricing produce.

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

#20

Post by gwillen »

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.)

I found at my old grocery store that self-checkouts had much better throughput than real lines due to self-selection. People who have many items, or who have coupons / are paying by check / need special help, will avoid the self-checkouts.
Post reply on HN