[GSlob]

The [blood] alcohol level sufficient to cause a [predetermined] degree of impairment is highly subjective- there must be people who are not to be trusted with driving at 0.05 and others on whom 0.25 would not show. Thus the tests measuring actual functioning and the degree of its impairment, along the line "walk straight" or measuring the reaction time - would be much more relevant than blood alcohol level.

[ASA Vet]

Some can do well on the tests too.

DUI Test