A shopping cart conveyor that inhibits the loading of a non-compliant shopping cart onto the conveyor. In one aspect, the invention provides a conveyor comprising a track operable to guide the shopping cart between a first location and a second location, a gate assembly including a door movable between a closed position inhibiting entry to the track and an open position allowing entry to the track, a lock for securing the door in the closed position, and a sensor (e.g., an ultrasonic sensor, an optical sensor, a radar sensor, an infrared sensor, an RFID reader, a magnetic sensor, and a mechanical sensor) positioned to detect the presence of a shopping cart. In another aspect, the conveyor is configured to move the gate from the closed position to the open position when the sensor detects the presence of a shopping cart. Preferably this is done using a drive mechanism coupled to the gate.