Why Alcohol Is Uniquely Dangerous

Run alcohol through the three stages and the reason it dominates crash statistics becomes clear — it attacks every stage at once:

Observe: alcohol impairs vision and slows the eye, narrowing the field further and degrading exactly the low-light and motion detection that Vision & Perception described.
Decide: the cruel part. Alcohol's first effect is loss of inhibition and overestimation of your own ability — the impaired driver feels more capable precisely as they become less. The stage that should catch the impairment is the stage alcohol disables first.
Act: slowed reaction time — lengthening every distance in Speed & Stopping Distances — plus degraded coordination and balance.

The trap is self-sealing: alcohol removes the judgement required to recognise you're impaired. "I feel fine to drive" isn't a lie the drinker tells other people; it's a lie the alcohol tells the drinker, by disabling Decide before anything else. That's precisely why the rule is a hard legal limit rather than "use your judgement" — the judgement is the first casualty.

Key takeaways

Alcohol degrades Observe, Decide and Act simultaneously — vision and eye speed, judgement and self-assessment, reaction and coordination
It disables Decide first, so the faculty that would notice the impairment is already gone — which is why the law sets a fixed limit instead of trusting self-assessment

Quick check

Why does the law set a fixed alcohol limit instead of asking drivers to judge whether they're fit to drive?

A) Because alcohol disables judgement first — the impaired driver genuinely feels more capable, so self-assessment is the one faculty you can't rely on

B) Because a fixed number is easier for police to enforce.

C) Because most drivers are dishonest about how much they've drunk.

D) Because judgement varies too much between individuals to legislate