I work in Grocery IT. We generally assume you have to have two self checkouts in order to meet the customer/item throughput of one staffed checkout. And even then, I'd tend to put my money on the staffed checkout.
Some of it is just the limitations of a SCO, in that store staff don't have to wait for each item to be weighed by the lane before moving to the next item, but a lot of is that most people are not nearly as fast as they think they are.
A lot of it depends on how hands-on the staff manning the SCOs are as well. The Costco near me implemented SCOs in the past year, but those might as well be full checkouts with the number of staff that are around them looking to help out.
Part of the problem is that the self checkouts are super paranoid about preventing theft. If you put your bag on the output you get in trouble, your child puts their hand on the scale you need cashier assistance, you don't wait long enough after the last item for it to be weighed and you need to start . It's literally impossible to go fast! I don't know if it is justified. But it seems surprising as I could easily just put something in my bag if I wanted to steal it, I don't know why I would bother putting it into the scale.
Of course the cashier will always be faster, they are familiar with the interface, know where most of the barcodes are and have the codes of most non-barcoded items memorized.
But self-checkout could be much faster by removing some anti-features (from the customer POV). I have seen a couple of stores with a better solution where you pick up a scanner at the start and scan your items as you go. This has the advantage of parallelizing most of the process instead of clogging up on big expensive machines. In fact with the ability to check out on that device you could probably get by with just a "Customer Service" desk for when something goes wrong.
In the Netherlands, self-checkout doesn't use scales. I simply scan all the items in my basket, and put them in my backpack immediately. Once in a while, you are flagged, and a sample of your items are scanned to make the probability low that you are stealing something. Scanning the loyalty card helps to prevent too many checks over time.
All in all, the total overhead next to scanning your items is a mere few seconds.
This is a huge contrast with my experience in the UK. Those scanners are talking, are slow to move between states, require you to put everything from one to another scale. This is indeed often slower than a human worker, and amazes me to no end.
That sounds way better, and quite possibly more effective at actually catching shoplifting. My experience in the UK, Ireland US and Canada has been the bad example as you have described.
It seems to be a classic case of bureaucratic risk aversion without proper cost analysis.
I much prefer self-checkouts because of the forced conversations cashiers are forced to have and cashiers just being bad at bagging, but they really do slow down the process. The scanner locks for a couple seconds after an item is scanned (even if there is no weight check or other delay screen), presumably to prevent double scanning for slower customers, but it just becomes a giant PITA when I have small items I could scan and toss into my bag in 10 seconds if they'd just remove the delay and it ends up being closer to a minute since it'll probably pause to reweigh a couple times in addition to the normal delay.
I avoid self-checkout at most stores because of this. Just too much a pain in the butt, never mind if I have a lot of items and they can't even fit in the baggage area!
Walmart has this figured out. You just scan the item. Done. No scales, no anti-theft I can tell aside from a person watching.
I remember Food 4 Less back in the day (maybe twenty years ago) having a sort of hybrid system where the cashier scanned your items and rang then up, but you bagged your own groceries.
Are you familiar with any similar systems today? How do they rate on throughput?
This is the it's always been done in Sweden. With space for two different customers to bag per cashier. A metal divider is put diagonally on the conveyor belt to feed items either left or right.
The 'metal divider, self bag' is a discount / bulk store I go to. Old-style 'casher + bagger' is another. And I've gone to stores with self-checkout, both with and without scales in them.
Seems quite varied here, with of course that variance mostly along franchise lines...
Any grocery store that’s understaffed/busy ATM. As awesome as H-E-B is, I’ve had to bag my own stuff once in a while. It usually feels a bit rushed and seems to annoy the checker if you’re not super-quick about it.
Some of it is just the limitations of a SCO, in that store staff don't have to wait for each item to be weighed by the lane before moving to the next item, but a lot of is that most people are not nearly as fast as they think they are.
A lot of it depends on how hands-on the staff manning the SCOs are as well. The Costco near me implemented SCOs in the past year, but those might as well be full checkouts with the number of staff that are around them looking to help out.