BAC is the blood alcohol content. In the State of ny the legal limit is .08
While the legal limit for DWI is .08, if an individual is below this limit they may still be charged with Driving While Ability Impaired, which is a violation in the State of New York, not a crime.
Suspension of license
In order to suspend your drivers license while your case is being prosecuted you MUST have a BAC above .08. If you do not, then your license can NOT be suspended while the prosecution of the case is ongoing... as a result for the most part it is not generaly adviseable to plead guilty early on such cases since you will retain yoru ability to drive throught the entire length of the case.
If below the legal limit there is greater than average potential to get an acquital after trial due to the smaller percentage of alcohol, generally the NYPD does not arrest individuals at .05 or below due to a general understanding of the margin of error of the machinery used ot measure BAC.