What is an example of a bad habit that indicates a lack of control while driving?

Making frequent lane changes without signaling is a significant indicator of a lack of control while driving. This behavior demonstrates a disregard for the rules of the road, specifically the importance of communicating intentions to other drivers. Signaling is crucial as it allows other motorists to be aware of a driver's upcoming actions, thereby reducing the risk of collisions caused by sudden lane changes. Frequent lane changes can create unpredictability in traffic, increase the chances of accidents, and highlight poor decision-making and situational awareness from the driver.

The other behaviors mentioned, while potentially problematic, do not directly indicate the same level of loss of control as failing to signal. Relying solely on mirrors can lead to blind spots but does not inherently convey reckless behavior. Failing to use the parking brake can be an oversight but isn't as immediately dangerous during active driving, and using cruise control in heavy traffic, while perhaps ill-advised, reflects more on a lack of situational appropriateness rather than a fundamental inability to control the vehicle.