Two Beers Before an 8 km Drive
A 65 kg man finishes dinner in Phnom Penh at 21:00. Over the previous two hours he drank two 330 ml cans of 5% beer. He ate a full meal and feels normal. At 21:30 he must drive 8 km home along Russian Boulevard. He has a valid Category B licence, and his car is in good condition. A friend says, “Two cans is nothing; food soaks it up.” He has no breathalyser. A police checkpoint is active about 3 km from the restaurant, and cars are being pulled aside. He considers waiting 20 minutes, drinking strong coffee, and then driving. He has taken no medicine or drugs. He weighs 65 kg, normally eliminates alcohol slowly, and must work at 07:00 the next day.
1. Is he legally fit to drive at 21:30? Explain using the limit and the effects of alcohol.
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- Cambodia's general blood-alcohol limit for ordinary drivers is 0.05% (50 mg/100 ml); professional or commercial drivers are subject to a lower limit. Two 330 ml cans at 5% contain roughly 26 g of pure alcohol.
- A rough Widmark estimate for a 65 kg man gives about 0.06% before elimination. After 1.5 hours, at roughly 0.015% per hour, the estimate is near 0.04%, but individual absorption, liver rate, and food make the range straddle 0.05%.
- Food and coffee do not speed elimination. Feeling normal is not a reliable guide because alcohol impairs judgement and reaction time before obvious symptoms appear.
- He cannot certify himself as legally fit. The safe and lawful decision is not to drive.
2. What is the safest plan for the 8 km trip?
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- Do not drive. Call a taxi or ride-hailing service, use a licensed friend who has not been drinking, or arrange delivery of whatever he needs.
- Waiting only 20 minutes is not enough. Elimination is slow and predictable only in broad terms; a short wait plus coffee does not remove alcohol.
- If he must retrieve the car, do it the next day after a long sleep and with no alcohol remaining. A 07:00 work start does not justify driving tonight.
- The checkpoint is not the main reason to avoid driving; the crash risk from impaired judgement and slowed reactions is the main reason.
3. At the checkpoint, what should he do if he has already driven?
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- Stop, stay calm, lower the window, and be polite. Present his licence, registration card, and identification if asked.
- Do not offer a bribe, do not flee, and do not refuse a lawful breath test. Refusing or bargaining usually makes the situation worse.
- If tested above the limit, accept the result and ask for the official penalty notice or receipt. Sign only documents he understands.
- The correct answer was prevention: a taxi would have avoided both the legal risk and the danger to others.