[Absolute driving incapacity at 1.0 promille--an erroneous limit]

Area of Science:

• Forensic Toxicology
• Traffic Safety Research
• Human Factors Psychology

Context:

• Current German legal driving limit (0.13% blood alcohol concentration) based on outdated literature.
• Debate exists regarding lowering the limit based on newer scientific interpretations.
• Previous legal decisions relied on laboratory studies, potentially overestimating impairment in real-world driving.

Purpose:

• To critically evaluate the scientific evidence for alcohol-induced driving impairment.
• To analyze the relationship between blood alcohol concentration (BAC), driving difficulty, and impairment.
• To provide evidence-based recommendations for legal alcohol limits in driving.

Summary:

• Empirical evidence shows no single BAC threshold for impairment; impairment is synergistic with driving situation difficulty.
• Significant impairments observed at lower BACs (0.07%) in complex driving scenarios, and below 0.05% in extreme conditions.
• Laboratory studies align with driving studies, indicating impairment is context-dependent.

Impact:

• Challenges the current fixed legal BAC limit in Germany.
• Suggests a revised legal limit of approximately 0.07% for average driving difficulty.
• Advocates for policy decisions on legal alcohol limits to consider situational driving complexity.