What is the presumptive level of alcohol concentration indicating a driver may not be under influence?

The presumptive level of alcohol concentration indicating a driver may not be under the influence is 0.05 or less. This lower threshold is significant because many jurisdictions recognize that drivers with a blood alcohol concentration (BAC) at or below this level are generally not considered impaired in their ability to operate a vehicle safely. This level is seen as a level below which impairment effects are unlikely to be significant in most individuals, meaning they can likely drive without experiencing significant impairments to their coordination, reaction time, and judgment.

In contrast, concentrations of 0.08 or more are typically associated with impairment and legal presumption of intoxication in many places. Similarly, levels like 0.06 to 0.07 are on the edge of impairment, and levels ranging from 0.09 to 0.10 clearly indicate a higher likelihood of significant impairment. Thus, 0.05 or less is the threshold that suggests a driver may not be under the influence.