BAC refers to a specific amount of alcohol within the bloodstream. If a driver is found to be operating a motor vehicle with more than .08% BAC, the driver could be arrested for a DUI / DWI offense.
When a driver is suspected to be driving while under the influence, police officers use specific technology to measure a driver's BAC levels. The most accurate way to measure the BAC level will be by utilizing a Breathalyzer or another form of chemical testing, such as a blood or urine sample.