Two Beers and a Prescription: The Math Before the Keys
A 150-pound driver has had two 12-ounce regular beers over about two hours at a friend's house and also takes a daily prescription antihistamine that carries a drowsiness warning. He feels 'fine' and estimates he is under the legal limit. He has a 20-minute drive home on mostly highway. He has not eaten much. He is 22 years old, so any alcohol in his system is illegal under the state's zero-tolerance rule for drivers under 21 - but he is over 21, so the adult limit applies. A friend offers to drive instead; he declines because 'it's just highway.'
1. Evaluate his 'I'm fine' judgment using the factors that actually determine impairment.
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Feeling fine is not evidence of being under the limit. Impairment depends on body weight, time, food, and the number and strength of drinks, and two standard beers in two hours for a 150-pound person puts blood alcohol in a range where judgment and reaction time are already affected, even if it may be under 0.08. Add an antihistamine with a drowsiness warning and the combined effect on alertness and reaction is greater than either alone. 'Mostly highway' is not safer: higher speeds mean less time to react and worse consequences. The correct call is not to drive.
2. What should he do, and what is the risk if he drives anyway?
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Accept the friend's offer or call a ride. The legal risk is a DUI arrest if his BAC is at or above the limit or if he is visibly impaired; the larger risk is a crash, because alcohol plus a sedating medication degrades attention, lane control, and braking reaction at exactly the speeds where margins are thinnest. Declining a safe ride to 'just take the highway' is the classic rationalization the exam is testing; the right answer is to separate drinking and sedating medication from driving entirely.