What does the term 'AUD' signify in vehicle inspections?

In vehicle inspections, the term 'AUD' typically signifies "Audible." This term relates to the audible signals or sounds that a vehicle may produce, which can be crucial indicators of various mechanical or operational issues. For instance, during an inspection, an auditor may listen for unusual sounds that could suggest problems with the engine, brakes, or suspension system. Recognizing and interpreting these audible signals is an important skill for inspectors, as they can help identify safety hazards or necessary maintenance before the vehicle is considered roadworthy.

The other choices present different meanings but do not pertain to accepted terminology in vehicle inspections, making 'Audible' the most relevant and accurate interpretation of the acronym in this context.