Night driving with sleep debt and a sedating antihistamine
A refrigerated semi-trailer is due to unload in Jeddah at 06:00. The driver left Riyadh at 18:00 after sleeping 3.5 hours in the previous 24, and took a sedating antihistamine tablet for an allergic reaction at 22:00. It is now 02:30 and he is 180 km from Jeddah on the highway. In the last 40 minutes he has yawned repeatedly, drifted across the lane line twice, opened the window, turned up the radio and drunk an energy drink. His eyes feel heavy and he cannot remember the last 20 km clearly. The dispatcher has called twice about the unloading slot and says the customer will charge a late fee.
1. Assess the driver's fitness to continue. Which factors combine here, and which observations are the most serious?
Read the worked answer
He is not fit to continue. Three factors are stacking: 3.5 hours of sleep in 24 is well below what a heavy vehicle driver needs; 02:30 sits in the early-morning low point of the body clock, when alertness is naturally lowest; and a sedating antihistamine taken four and a half hours earlier can still cause drowsiness and impair reaction time and attention.
The most serious observations are the two lane drifts and the missing 20 km of memory. Those are not warning signs to be managed with a window and a radio - they indicate he has already had microsleeps. Yawning and heavy eyes confirm the trend. The energy drink may give a brief lift, but it does not restore performance, and once it wears off the impairment is worse. The late fee is a commercial matter and carries no weight in the fitness decision.
2. What should he do now, and why are coffee, fresh air and the radio not a solution?
Read the worked answer
He should stop at the next safe place - a lorry park, service area or truck stop, not the hard shoulder - and sleep. A nap of at least 20-30 minutes will reduce immediate sleepiness, and a coffee taken just before it can help briefly after waking, but neither replaces proper sleep. If that means missing the 06:00 slot, the slot is missed.
Coffee, fresh air and loud music only mask symptoms for a short time; they do not reverse sleep debt or the sedating effect of the antihistamine, and they can create a false sense of being alert. If there is nowhere safe within a short distance, he should slow down, keep right, and take the first exit rather than pushing 180 km on willpower. He should also check with a pharmacist or doctor about the antihistamine and avoid taking a sedating one before driving again.
3. What should he say to dispatch, and what are the consequences of continuing?
Read the worked answer
He should state plainly that he is too tired to drive safely, that he has already drifted and lost awareness of the road, and that he is stopping at the next safe place. Ask dispatch to notify the customer and rebook the unloading slot, and record the call time and content.
Company pressure does not transfer the legal duty: the driver is responsible for not driving when unfit, and a crash caused by a fatigued driver exposes him and the company to serious consequences, including criminal liability and insurance refusal. If dispatch pushes back, he should ask for a relief driver or written permission to park and escalate to the transport manager. Declaring a sedating medication is also part of fitness for duty and should be reported before the next shift, not after an incident.