Two blood alcohol limits
| Who | Limit |
|---|---|
| Learner, novice and professional drivers | 20 mg per 100 ml of blood |
| Everyone else | 50 mg per 100 ml of blood |
The 20 mg limit is effectively zero — a single drink can breach it. A novice driver is anyone in the first two years after passing their test.
Even the general 50 mg limit is stricter than the 80 mg that applies in Britain and Northern Ireland, which is worth knowing if you learned to drive there.
Nothing sobers you up except time
Not coffee, not a cold shower, not food. Your liver clears alcohol at its own pace and nothing speeds it up. Strong coffee produces an alert drunk, which is more dangerous than a sleepy one, because it removes the only warning sign you had.
This is why the morning after is a real and frequently prosecuted offence. If you drank heavily until the early hours, you may still be over the limit at breakfast. If in doubt, do not drive.
Checkpoints
Mandatory alcohol testing checkpoints have operated since 2006 and require no suspicion at all — a Garda does not need a reason to stop you and test you. Refusing to provide a sample is itself an offence, and carries penalties comparable to failing the test.
Drugs, prescribed included
Driving impaired by any drug is an offence, whether or not a doctor prescribed it. If a medicine warns about drowsiness, ask your pharmacist whether it is safe to drive on. Roadside drug testing has operated since 2017.
Fatigue
The warning signs are: difficulty keeping your eyes open, drifting within the lane, and not remembering the last few kilometres. Micro-sleeps of a few seconds happen without you noticing them.
Opening a window and turning up the radio does not treat fatigue — it masks it for a few minutes. What genuinely works is stopping somewhere safe, a caffeinated drink, and a 15 to 20 minute nap.