Which behavior is a common sign of impairment that officers look for during a traffic stop?

Erratic driving behavior is often a definitive indicator of impairment that law enforcement officers use to assess a driver's condition during a traffic stop. This behavior can manifest in various ways, such as swerving in and out of lanes, sudden acceleration or deceleration, or inconsistent speed. These actions are not consistent with safe driving practices and suggest that the driver may be having difficulty with their motor skills or judgment, which are common effects of alcohol or drug impairment.

The presence of erratic driving raises immediate concern for the safety of the driver, passengers, and other road users, prompting officers to intervene. Observing such behavior helps the officer establish reasonable suspicion that the driver may not be operating the vehicle safely due to impairment.

In contrast, behaviors such as using turn signals, driving at the speed limit, or frequently changing lanes do not indicate impairment and may suggest that the driver is adhering to traffic regulations. While frequent lane changing might be questionable, if done responsibly and safely, it wouldn't be a primary indicator of impairment in the same way that erratic driving would be. Thus, erratic behavior stands out as a key sign for officers in identifying potentially impaired drivers.