A user interface device for an autonomous vehicle (AV) can include an autonomy engage selector and a plurality of vehicle interfaces connected in series. Each of the plurality of vehicle interfaces can correspond to a respective vehicle operation and can include a relay that engages when the vehicle interface is in a ready state. The user interface device can also include a drive-by-wire controller to autonomously operate each of the plurality of vehicle interfaces in response to an engage input on the autonomy engage selector when the user interface device is in a ready condition.