Autonomous systems are usually measured by the degree to which humans are involved in the system, often starting a level 0 autonomy which requires full human involvement to the highest level of autonomy for a given system, usually at least 3 or more levels. For example, autonomous vehicles have six levels of autonomy with Level 0 being fully operated by a human to Level 5 autonomy requiring no human involvement. Levels 1-4 having varying degrees of autonomous operation.