Grocery Cart Security

I went grocery shopping at a new Shoppers in Laurel today. One of the great things about shopping at a new store is that all of the carts still function properly. But I noticed a sign inside my cart as I was leaving. It said "This cart locks up outside the boundaries of the parking lot." I looked at the wheels and, sure enough, the front right wheel was different from the others. It must have some kind of breaking mechanism inside it that's trigger when it crosses the boundary, much like those dog collars that shock the dog when he tries to leave the yard. It's rather sad that this security feature is necessary, but perhaps too many drunks were tempted to use them as modes of transportation.