Shopping trolley customized for different designs

Most retailers in North America utilize a cart retrieval service, which collects carts found off the store's premises and returns them to the store for a fee. The primary strength of this system is the ability of pedestrian customers to take purchases home and allow retailers to recapture abandoned carts in a timely manner at a fraction of the cost of a replacement cart. It also allows retailers to maintain their cart inventories without an expensive capital outlay. A drawback of this method is that it is reactive instead of proactively preventing the carts from leaving a parking lot.

Electronic systems are sometimes used by retailers. Each shopping cart is fitted with an electronic locking wheel clamp, or 'boot'. US Patent No. 5598144A. A transmitter with a thin wire is placed around the perimeter of the parking lot, and the boot locks when the cart leaves the designated area. Store personnel must then deactivate the lock with a handheld remote to return the cart to stock. Often a line is painted in front of the broadcast range to warn customers that their cart will stop when rolled past the line. However, these systems are very expensive to install and although helpful are not foolproof. The wheels can be lifted over the electronic barrier and/or pushed hard enough that the locks break. There are also safety concerns if the person pushing the trolley is running, & also if the trolley doesn't lock & is taken onto a road, locking due to magnetic materials under the road. Some cities have required retailers to install locking wheel systems on their shopping carts. In some cases, electronic systems companies have encouraged passage of such laws to create a captive audience of potential customers.