What term describes the ability to operate the vehicle unsupervised?

The term that best describes the ability to operate a vehicle unsupervised is proficiency. Proficiency indicates a level of skill and competence that allows an individual to perform tasks reliably and effectively without the need for oversight. In the context of driving, particularly when it comes to operating a school bus, proficiency encompasses not only the basic skills of driving but also an understanding of safety protocols, traffic laws, and the ability to respond effectively to dynamic situations on the road.

While competence refers to having the necessary ability or skills to perform a task, proficiency implies a higher level of mastery and confidence in executing those skills independently. Authorization relates to being given permission to act, which does not necessarily imply that one has the skill to operate a vehicle safely and effectively. Expertise suggests a deep and extensive knowledge of a subject, which may not directly correlate to unsupervised operation of a vehicle in practical terms. Thus, proficiency is the most suitable term as it embodies the independence and skill required to operate a vehicle without supervision.