Stop & Shop tries to curb late-night joyriding down Southie sidewalks

I believe these systems work on the same principle as the invisible fence for dogs -- a buried wire emits a radio signal, and if the receiver gets close enough for the signal strength to reach a certain threshold, it activates. Lifting the cart up a foot or two shouldn't work, since the activation zone should be of a pretty decent width. But perhaps the wire has been damaged and is not emitting as strong a signal as it is intended to. At the Star Market in Porter Square, I think I've noticed where the pavement has been cut for the wire to be laid in, and along Elm St there's an exposed wire in a plastic tube. It would be easy for that to be partially damaged.

Shielding around the wheel might allow bypass. Or perhaps not. I wonder if it uses the frame of the cart as an antenna?

(I recall that at least one person claims to have recorded the lock and unlock signals and broadcast them at high gain on an antenna, playing a pretty rude game of red-light-green-light with all carts in range. I can't condone this, but it's quite the mental image. I also am not sure I believe it, since the cart I illicitly unlocked for fun required a mechanical action simultaneous with the unlock radio signal.)

Grocery carts cost something like $200–250 each, so it could add up. I don't have a strong sense of how many of the joyridden carts were being recovered, how much it cost to recover them, whether there was damage that needed repair, how many were being stolen by the homeless, how many were stolen/abandoned by people who live an awkward number of blocks away and wanted to get a large number of groceries by foot, etc.

I would guess that the total yearly loss was marginally less than the amortized cost of a theft-prevention system and that this recent outcry just tipped the balance over in favor of installing one. But it's pretty hard to guess what the breakdown was.

But the local teens might get bored enough to stockpile them on the beach.