Which of the following is an indicator of drug impairment during a traffic stop?

Erratic driving behavior is a significant indicator of drug impairment because it suggests a loss of motor control and decision-making abilities that can be associated with the influence of drugs. When a driver exhibits erratic driving—such as swerving, sudden stops, or inconsistent speeds—it raises red flags for law enforcement that the individual may be under the influence.

Other options, such as a calm demeanor, cooperative behavior, and clear speech, do not strongly suggest impairment. In fact, a calm demeanor or cooperative behavior could indicate a driver is in control of the situation, and clear speech suggests that they are not experiencing cognitive impairment. Therefore, erratic driving behavior stands out as a key sign that a driver's abilities may be compromised due to drug use during a traffic stop.