Two beers, four hours' sleep and an antihistamine
At 04:50 you are due to drive 160 km from Bamako to Ségou, with three passengers, to arrive by 08:00. You finished two 33 cl bottles of beer at 23:00, slept from 23:30 to 03:30, and took an antihistamine at 04:00 for a bad allergy. You have had one coffee and feel 'fine'. Your eyes are gritty, you yawn, and you have already misread a road sign once. The route is mostly two-lane RN6 with village crossings, some unlit stretches, and a known checkpoint. Your passenger offers to drive but has a licence and has slept six hours. You have no breathalyser. You are 38 years old, weigh about 75 kg.
1. Assess your fitness to drive at 04:50, separating alcohol, fatigue and medication.
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Alcohol: two 33 cl beers at 5% contain roughly 26 g of pure alcohol. For a 75 kg man the peak blood alcohol would be in the region of 0.4–0.5 g/L, but five to six hours have passed. It is likely that most has been eliminated, but you cannot assume zero: elimination varies, and you have no breathalyser. Any residual alcohol is a legal and safety risk. Do not drive on a guess.
Fatigue: four hours' sleep, waking at 03:30, and driving through the 04:00–06:00 circadian low is a serious impairment. Gritty eyes, yawning and misreading a sign are warning signs of falling performance, not proof that you are 'fine'. A 160 km drive with village crossings demands sustained attention.
Medication: an antihistamine taken at 04:00 may be sedating, especially older types. Driving while impaired by medicine is still impaired driving. The combined effect of short sleep and a sedating drug is greater than either alone.
The honest assessment is: not fit to drive at 04:50.
2. What is the safest plan, and how do you handle the passenger's offer?
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Accept the offer unless there is a reason the passenger is also unfit. The passenger has a licence and six hours' sleep, which is a better starting point than your four hours plus medication.
Safest plan:
- Hand over the keys before leaving, not after you feel drowsy on the road.
- Check the passenger has not been drinking and is not taking sedating medicine.
- If the passenger is unsure, delay the trip or use public transport. Arriving late is better than a head-on crash on the RN6.
- If you must travel as a passenger, do not 'help' by staying awake and distracting the driver; sleep if you can.
Handling the offer: be direct. Say you took an antihistamine, slept four hours and misread a sign. Do not let the 08:00 deadline turn a bad decision into a shared one. The schedule is not a legal defence.
3. If you do drive, which countermeasures are unreliable, and why?
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Unreliable countermeasures:
- Coffee and energy drinks mask drowsiness for a short time but do not restore reaction time or prevent microsleeps.
- Cold air, loud music, open window create a temporary alerting effect that fades.
- Slapping your face or talking to passengers do not prevent a microsleep.
- 'I will stop if I feel tired' fails because drowsiness impairs the ability to judge your own drowsiness.
- Pushing through because the checkpoint or arrival time is fixed adds schedule pressure, which encourages speeding.
Reliable measures are sleep and rest: a planned 20-minute nap in a safe place, sharing the driving, or delaying the journey until the antihistamine effect has worn off. Even then, four hours' sleep is short; a nap before departure is not the same as a full night's sleep. The correct decision remains not to start the drive impaired.