Evan Schuman's StorefrontBacktalk

Unfortunately, cameras can’t replace the other functions of that self-checkout associate. Those include age verification and dealing with items that scan with a different price from the shelf tag, but become even more important when the technology just doesn’t do what the customer expects.

For example, big-ticket, full-cart shoppers who haven’t spent much time doing self-checkout because they’ve always had too many items could be in for a shock. Coupons may or may not be supported at self-checkout. If they are, figuring out why a particular coupon has been rejected is often a challenge for experienced cashiers, never mind self-service newbies.

Wrinkled barcode labels on vegetables or flexible packaging are a problem for human cashiers, as well, but they have the experience to know when to quit and key in the number. Dropping that problem on inexperienced customers could generate a whole new level of frustration. Double-scanned items and the need for overrides have the potential to push confusion and irritation even higher—something that’s already a problem with conventional self-checkout.

And then there’s intentional vandalism. And customers who unintentionally damage equipment with spills, for example, but then don’t clean up or call for help out of embarrassment. Even without damage, some customers are simply messy. (How often do you hear “Clean up in aisle 5?” That’s about how often you can expect to hear “Clean up on lane 23” going forward.)

Even without messy customers, all horizontal scanning windows require occasional wiping down or performance degrades. Human cashiers do that routinely. If some associate isn’t handling that task, the hybrid checkout won’t stop working—it will just begin to work poorly, and customers like intermittent problems just about as well as IT people do.

All that comes down to a simple reality: Asda has tested with four hybrid checkout lanes. When it expands to dozens of lanes, there will still have to be an associate nearby to help—but that associate might be 20 lanes away instead of a few steps away. This isn’t going to save nearly as much in associate time as Asda—or the chain’s owner Walmart—might hope.

Some of the problems might go away with a switch from barcodes to RFID tags for product identification. That likely won’t happen soon enough to affect Asda’s ongoing implementation of hybrid lanes or any decision by Walmart to try it in its own stores.

In the meantime, this is clearly not something grocery chains can afford to think of as just more self-service lanes. If customers like them, this could wipe out most of the assumptions chains have depended on about self-checkout.

Not to mention some associates who are going to get a lot more exercise.