Alcohol, drugs and driver fatigue
Alcohol and drugs
The adult legal limit is 50 mg of alcohol per 100 mL of blood, or 250 micrograms per litre of breath. If you are under 20, the limit is zero. Illegal drugs and some prescription medicines impair judgement, reaction time and balance; do not ride if affected. Police can require a breath or blood test after a crash or when they suspect impairment.
Fatigue
Fatigue slows reactions and makes you miss hazards. Take a break at least every two hours, share long rides, and stop when you feel drowsy. Coffee and fresh air do not remove alcohol or cure fatigue; only time lowers blood alcohol.
Worked example
A 19-year-old rider has one standard drink at a party and feels fine. The legal limit for under-20 riders is zero, so they must not ride. Feeling fine is not the test.
Traps that cost marks
Thinking coffee, food or a cold shower sober you up. Assuming prescription medicine is always safe to ride on. Pressing on when tired because the destination is close. Forgetting that the zero limit applies to riders under 20.