23 CFR § 1210.3
Definitions
May 21, 2020
As used in this part:
(a) Alcohol concentration means either grams of alcohol per 100 milliliters of blood or grams of alcohol per 210 liters of breath.
(b) BAC means either blood or breath alcohol concentration.
(c) Operating a motor vehicle means driving or being in actual physical control of a motor vehicle.