Locking shopping cart?

Amber and I were at Kroger a couple of weeks ago, and this sign was affixed to the interior of our shopping cart.

Shopping Cart Sign

A quick inspection of the cart yielded no interesting looking mechanics, antennae, or even devices that appeared to be capable of locking the wheels. Any theories as to how this would work?

Published by Waldo Jaquith

Waldo Jaquith (JAKE-with) is an open government technologist who lives near Char­lottes­­ville, VA, USA. more »

10 replies on “Locking shopping cart?”

  1. I experienced this while living in DC at Safeway. One front wheel had a rather large enclosure and it appeared to be triggered by something sub-terranean. I lived two blocks away and wanted to push the cart to my house and then take it back, but alas, that wasn’t possible. I crossed some barrier and the wheel locked up. At the time I suspected that it worked via magnetism, but I’m really not sure.

  2. My theory is the same as yours, Shaula — I’ll bet that they have no such barrier at all.

    Next time I’m there, I’ll have to investigate all four wheels, Duane. I only looked at a couple, assuming that the locking device would affect all wheels. Of course, now that you point it out, it’s clear to me that only one has to be locked up to keep the cart from going anywhere. :)

  3. I’ve noticed the same thing at several stores. I inspected all the wheels, and uncovered nothing that looked as if it would be capable of stopping the cart. In fact, they just looked like your everyday run-of-the-mills grocery carts, save the sign of course. I wanted desperately to put them to the test, but the fear of someone seeing me take a handlebar to the stomach won out in the end.

  4. Given Steve’s reply, I would side with the social engineering perspective. At Shaw’s (New England grocery store chain) in North Providence, RI, they have similar signs, and the front left wheels of each cart has a fairly obvious black plastic covering. I’ve not tested the carts myself, but the myriad of carts littered along the edges of the yellow line marking the boundary suggests that they in fact work.

    It seems to me, however, that if you’re willing to lift the front of the cart the entire way home, or wherever you’re going, then it would be simple to take the cart. And this is assuming that the wheel has to be in close proximity to actually work and you couldn’t simply break the barrier and be home free. This is, of course, easier said than done with a full shopping cart.

  5. I can’t tell you all how delighted I am to read the great mental powers being lended to the question of how to hijack a shopping cart. :)

    Back to the invisible pet fence theory…there might be a boundary that emits a special high frequency noice, to which only shopping carts are averse. Maybe.

  6. This is kind of funny to see people speculating about the mechanics of the locking shopping cart, because I’m the service coordinator for a company that manufactors such a product. The one you’re looking at is Gatekeeper, our competitor. I found this page because OUR product, the Carttronics CAPS (Cart Anti-Theft Protection System) caster, was recently featured on CSI: Miami and I was wondering if any viewers out there were talking about it.

    To satisfy your curiosity, here’s the link to Gatekeeper’s site: http://www.gatekeepersystems.com/gs1work.html

    One difference between the caster we sell and theirs is that ours has a shell with a skid plate that comes down to stop the cart from moving. Gatekeeper’s locking mechanism isn’t visible, so a lot of times those mobile cart collectors will round up locked up carts and wear out the mechanism. That’s all.

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