The U.S. government granted Walmart a patent last week that hints at the company planning to roll out a system that allows shopping carts to drive themselves.

According to the patent request, the carts will be equipped with detachable motors that have sensors and video cameras. Customers will be able to request a cart using a "user interface device" and the motors will be able to fetch a cart and bring it to a customer. The system will also be able to identity an unattended shopping cart in a store or parking lot and return it to a docking station, according to the request.

The system also may help the stores inventory as one portion of the filing describes a scenario in which the system receives a request for an item, searches an inventory database and then sends the cart to a store shelf to make sure the item is there.

There is no word on when or where Walmart intends to start using the system.