Commercial Driver License (CDL) Class B Practice Test

Yawning frequently is a well-known physical indicator of drowsiness. It is a natural reflex that helps to increase oxygen intake and stimulate the brain, often occurring when the body is fatigued or in need of rest. When a driver starts yawning often, it typically signifies that they are not fully alert, which can impair their ability to respond to road conditions effectively. On the other hand, rapidly checking mirrors might indicate a heightened sense of alertness or could be a habitual behavior to maintain awareness of the surrounding environment, rather than a sign of drowsiness. Maintaining a constant speed is an essential part of safe driving and does not necessarily reflect the driver's level of alertness. Listening to music loudly can sometimes be used to stay awake; however, it may also lead to distractions, which is not an effective measure of drowsiness.