Wal-Mart plans self-driving shopping carts

Wal-Mart Stores Inc. is working on self-driving shopping carts that would roam stores and herd themselves out of the parking lot.

A patent granted to the retailer last week by the U.S. government indicates the carts would be equipped with detachable motors that have sensors and video cameras.

Customers could call the carts using a user interface device, possibly a smartphone.

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