A control knob assembly for a cooktop appliance includes a control knob having a plastic outer shell defining a cavity and a boss extending from the outer shell through the cavity. A steel weight is positioned within the cavity around the boss for adding mass to the control knob and a locking mechanism, such as a lock washer, is positioned around the boss to secure the weight within the cavity.

In order to provide a fail-safe operating mode during a transition between an autonomous steering mode and a driver-controlled steering mode in an emergency situation, a steering system comprises a steering shaft, a brake mechanism movable between an released position and a engaged position for angularly locking the steering shaft, and an override such that a non-destructive external torque applied to the steering shaft above a given threshold when the brake mechanism is in the engaged position results in a rotation of the steering shaft.