Oddly, underage refers not to driving before the legal age, but drinking before the legal age. Alcohol purchase and posession laws would seem to preclude "underage drinking" and therefore "underage drunken driving." However, states pass laws limiting BAC for underage drunken drivers above 0.0% (often at 0.08%). Perhaps this is a commetary on the legal system's opinion of the baseline capacity of teen drivers.... Less alcohol need be present to define an underage drunken driver as too impared to drive. --[Branteaton]]