Driver Fitness, Fatigue, Alcohol and Drugs
Fitness to drive is a legal and medical concept. The Austrian alcohol limit for novice and professional drivers is 0.1 g/l (effectively zero), and 0.5 g/l for other drivers; from 0.8 g/l the offence becomes serious, and refusal to take a breath or blood test carries heavy penalties. Drugs and medicines that impair driving are prohibited regardless of prescription; read the package warning. Fatigue is the most underrated impairment: microsleeps at speed cause severe crashes, and the only cure is a break or sleep, not coffee or fresh air.
Know the medical fitness categories: eyesight requirements, the obligation to report conditions that affect driving, and periodic checks for higher categories and older drivers. Illness, stress, strong emotion and certain medicines (antihistamines, sedatives) reduce fitness. The exam also tests first-aid obligation and the rule that you must not drive if you cannot control the vehicle safely.
Traps: questions implying coffee or open windows cure fatigue (they do not); assuming a prescription makes a medicine safe to drive with; assuming the 0.5 limit applies to probationary drivers (it does not).
Worked rule of thumb: plan a 15-minute break at least every two hours, and stop immediately at the first signs of tiredness - yawning, heavy eyelids, drifting, missed signs. Alcohol is eliminated at roughly 0.1–0.15 g/l per hour, so there is no safe shortcut to sobering up.