What should be checked regarding the mirrors during pre-trip inspection?

During a pre-trip inspection, ensuring that the brackets of the mirrors are securely mounted is essential for safety and effective vehicle operation. If the brackets are loose or damaged, it could lead to mirrors shifting during transit or becoming completely detached. This can significantly impair the driver's ability to see other vehicles or obstacles, which heightens the risk of accidents.

Each of the other aspects related to mirrors, while important, does not directly address the structural integrity that is vital for their functionality. For instance, adjusting the mirrors correctly ensures the driver has optimal visibility, while having them clean is also crucial for reducing blind spots. However, if the brackets are not properly secured, adjustments or cleanliness will not matter, as the mirrors could fail to hold their position. Heated mirrors are beneficial in certain weather conditions, but they are not a universal requirement or focus during a routine pre-trip inspection. Therefore, checking that mirror brackets are securely attached takes precedence as a critical safety measure.