What is a common indicator of impairment during a traffic stop?

Failure to maintain lane position is a recognized indicator of impairment during a traffic stop. When a driver is under the influence of alcohol or drugs, their motor skills and cognitive functions can be significantly compromised. This often leads to difficulty in controlling the vehicle, which can manifest as drifting into other lanes, making sudden lane changes, or not staying centered in the lane. Law enforcement officers are trained to observe these behaviors as signs that a driver may be impaired.

In contrast, waving arms while speaking may indicate excitement or an animated conversation but does not directly correlate with the ability to operate a vehicle safely. Using turn signals correctly reflects a driver's adherence to traffic laws and does not indicate impairment. Similarly, driving below the speed limit may not be an accurate sign of impairment; some drivers might choose to drive slower for a variety of reasons unrelated to alcohol or drug influence.

Therefore, the best indicator of impairment in this context is the failure to maintain lane position, which directly relates to a driver's ability to navigate the roadway safely and effectively.