Some places with shopping carts have an "invisible fence" that locks up one of the wheels of the cart when you push the cart outside the property. These are us

Some places with shopping carts have an "invisible fence" that locks up one of the wheels of the cart when you push the cart outside the property. These are usually marked with a yellow line on the ground. I presume they use some kind of RF field with an underground wire. Maybe that Safeway has some issues with theirs.