Which behavior indicates a high risk of driver fatigue?

Answer: C — Sudden changes in speed or direction

Sudden changes in speed or direction are indicative of driver fatigue because they can be a sign that the driver is not fully attentive or is experiencing lapses in concentration. When an individual is fatigued, their reaction times slow, leading to erratic driving behaviors such as unplanned speed adjustments or abrupt turns. A fatigued driver may struggle to maintain a steady course or speed, which increases the risk of accidents. In contrast, frequent stops for rest suggest a proactive approach to managing fatigue, while consistent speed maintenance reflects a stable level of alertness and control. The use of cruise control typically promotes a steady driving pace and lessens the physical demands on the driver, which can help combat fatigue. Therefore, sudden changes in speed or direction stand out as a clear warning sign of potential fatigue-related issues on the road.