According to NHTSA, which is considered a driving clue of impairment?

Weaving is recognized as a significant driving clue of impairment because it typically indicates that a driver is having difficulty maintaining a straight path on the road. Impaired drivers may struggle with coordination and balance, leading to erratic steering behaviors, such as weaving within their lane or across lanes. This behavior can stem from the influence of alcohol or drugs, which can affect a person’s motor skills and judgment.

In the context of impaired driving detection, law enforcement agencies and the National Highway Traffic Safety Administration (NHTSA) look for these observable signs to assess a driver's level of impairment. Other behaviors like speeding and frequent lane changes can occur as well but are not as definitive in indicating impairment compared to weaving, which is a direct observation of a driver’s inability to control their vehicle effectively. The absence of headlights is also a concern, but it may not directly reflect the same level of impaired control that weaving does.