What is the blood-alcohol concentration (BAC) at which it is illegal for an adult driver to operate a motor vehicle in Illinois?
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A.
.05%
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B.
.04%
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C.
.08% Correct
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D.
.10%
The answer is ".08%"
Illinois's per-se BAC limit is .08% or more for drivers 21 and older, and that number alone is enough to convict. You can still be convicted of DUI below .08% if your driving ability is impaired. Picking .10% leans on the older federal cutoff instead of the .08% Illinois currently sets for adult drivers.
The traps in the wrong answers
A. .05%
Illinois's per-se threshold is .08%, not .05%. The manual notes alcohol impairs driving below .08%, but the per-se line still sits at .08%. Treats the point where alcohol starts affecting driving ability as the per-se legal threshold.
B. .04%
Illinois's per-se BAC for a standard driver's license is .08%; .04% is the federal commercial-driver limit. Confuses the federal commercial driver's license threshold with the rule for a regular passenger license.
D. .10%
Illinois's per-se BAC is .08%, not .10%. Carries the older federal .10% cutoff forward instead of using the current .08% per-se rule.
This question tests your knowledge of DUI & Impaired Driving in Illinois. Source: Illinois Rules of the Road, "Blood-Alcohol Concentration (BAC)/Presence of Drugs," p.48..
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