Two beers, a cold and a probationary licence
It is 23:15 on a Friday in December. You have held a category B licence for 14 months, so you are still inside the three-year probation period. At a birthday party you drank two 0.5-litre beers at 5 % vol between 19:30 and 21:30, and you ate a plate of pasta. Because of a heavy cold you took a cetirizine tablet at 22:00; the leaflet warns that it may cause drowsiness and that you should not drive if affected. You weigh 72 kg. The way home is 9 km through two villages and one unlit stretch, and you know that the police regularly run breath-test checkpoints on the main road on Friday nights. You have yawned repeatedly and your eyes are burning. A friend says: 'Two beers is nothing, and it is only nine kilometres.'
1. What alcohol limits apply to you, and is it plausible that you are above them? Show the estimate.
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The limits. For an experienced driver the limit is 0.5 per mille blood alcohol (0.25 mg/l breath). As a holder still inside the three-year probation period you are subject to 0.1 per mille (0.05 mg/l breath) - effectively zero tolerance in practice. The same 0.1 per mille applies to professional drivers.
The estimate. Two 0.5 l beers at 5 % vol contain about 2 × 20 g = 40 g of pure alcohol. Using the Widmark approach with r ≈ 0.7 for a man: 40 / (72 × 0.7) ≈ 40 / 50.4 ≈ 0.79 per mille as a peak. Between 21:30 and 23:15 is 1.75 hours, and the body eliminates roughly 0.1–0.15 per mille per hour, so about 0.2–0.25 has gone: you are plausibly around 0.5–0.6 per mille now, possibly at your peak depending on how fast you absorbed it.
Conclusion. That is over the ordinary 0.5 limit and five to six times over your 0.1 limit. Even one beer would already breach 0.1 per mille. This is not a borderline calculation; the answer is no driving at all.
What does not help. Pasta, coffee, water, a cold shower or fresh air do not remove alcohol. Only time does.
2. How does the medication change the picture, and what does Swiss law say about driving when you are not fit?
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Separate offence. Alcohol is not the only issue. Under Art. 31 of the Road Traffic Act a driver must be fit to drive, and Art. 91 makes driving while unfit punishable even when you are below an alcohol limit. Fitness is assessed on your actual condition, not only on a number.
The tablet. Cetirizine is a sedating antihistamine; the leaflet explicitly warns of drowsiness and tells you not to drive if affected. You already are affected: yawning, burning eyes, a heavy cold. Alcohol and a sedating antihistamine act on the same system and their effects combine more than proportionally - the classic 'one beer and one tablet' case.
The time of day. 23:15 is inside the circadian low, when alertness drops naturally; add a cold and a warm car and the risk of a micro-sleep on the 9 km is real, not theoretical.
Practical test. You cannot certify your own fitness when the warning is on the leaflet and you have the symptoms. The correct conclusion is that you are unfit on two independent grounds, either of which alone would be enough to make the drive illegal and dangerous. A doctor or pharmacist should be asked about a non-sedating alternative for next time - not tonight.
3. Your friend pushes you to drive. What do you say, what do you actually do, and what would the consequences have been?
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The argument. 'Only nine kilometres' is the weakest possible argument: most alcohol-related crashes happen on short, familiar, local journeys, precisely because familiarity lowers vigilance. The checkpoint is a secondary issue; the primary one is that a 9 km village route at night has pedestrians, unlit crossings and parked cars.
What you do. Hand over the keys or put them away, take a taxi or the night bus, sleep at the host's place, or call someone who has drunk nothing. Arrange it before the argument, not after it. If you have already driven, do not 'drive home quickly to be safe' - leave the car and collect it the next day.
Consequences if you had driven. At 0.1 per mille and above, a probationary driver commits a serious offence: the licence is withdrawn (a minimum withdrawal period applies, not a warning), the probation period is extended, and there is a criminal complaint under Art. 91 plus a fine. On top of that, an insurer can claim recourse for damage caused while unfit to drive, and a learner or probationary driver may be required to retake the practical test afterwards. That is the real price of nine kilometres.