Tiredness, Medication and the Night Trunk Route
A driver on a regular night trunk from Sofia to Varna (about 380 km each way) reports to you at 18:00. He slept from 23:00 to 04:30, then drove his children to school and did household errands. He has a mild cold and has taken a pharmacy cold remedy containing a sedating antihistamine, one dose at 12:00 and a second planned for 22:00. He says he feels fine and has done this run for eleven years. The route is mostly two-lane road with a monotonous 90 km section, and the forecast is for fog after midnight with visibility down to 80 m in places. His tachograph shows 41 hours of driving in the last seven days.
1. Identify the fatigue and fitness-to-drive risks in this scenario and decide whether he should start the shift.
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Several risks compound each other.
- Sleep: 23:00–04:30 is 5.5 hours, below the 7–9 hours most adults need, and the period 04:30–18:00 contains no further sleep. By 02:00–04:00 he will be at roughly 21–23 hours awake, deep in the circadian low, when the body's drive to sleep is strongest.
- Medication: sedating antihistamines impair reaction time and cause drowsiness, and the effect is additive with sleep loss. A second dose at 22:00 would put peak sedation squarely in the night driving period. Many such medicines carry a warning about driving; the driver must not drive if affected.
- Monotony plus fog: a 90 km featureless stretch at night, with visibility down to 80 m, removes the stimulation that keeps a tired driver alert and simultaneously demands more attention and lower speed.
- Habit: eleven years of doing the run is not evidence of safety - it is evidence of exposure. Experienced drivers underestimate their own impairment.
Decision: he should not take the vehicle. The combination of short sleep, a sedating medicine with a further dose due, and night fog is a foreseeable accident. Substitute a rested driver, or delay the departure until after a proper sleep period and once the fog clears. Record the reason.
2. If a relief driver is not available and the load is urgent, what controls would you put in place, and how would you adapt driving to the fog?
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Controls, in order of effectiveness:
- Eliminate: delay departure until morning, when the driver has slept and the fog has lifted; the circadian low has passed.
- Substitute: use a rested driver, or split the run between two drivers at a mid-point.
- Reduce exposure: cancel the second dose of the sedating medicine and switch to a non-sedating alternative after consulting a pharmacist; no alcohol; a proper meal and hydration.
- Planned breaks: a break of at least 15 minutes every two hours, taken in a lit area where he can walk around, in addition to the statutory 45 minutes after 4 h 30 min. A short nap of 15–20 minutes before the worst hours is far more effective than caffeine alone.
- Monitoring: a phone check-in at each scheduled stop, and authority for the driver to stop and rest without penalty.
Driving in fog at 80 m visibility:
- Reduce speed so that you can stop within the distance you can see to be clear; at 80 m this means well below the motorway limit, and on a two-lane road, often 50 km/h or less.
- Use dipped headlights and fog lamps where fitted; do not use main beam, which reflects back.
- Increase the gap to several seconds, avoid overtaking, and be ready for stationary or slow traffic and unlit vehicles.
- Use the road markings and the right-hand edge as a guide, and be prepared to pull into a safe lay-by if conditions worsen rather than pressing on.