The 20 Questions Everyone Gets Wrong on the Irish Theory Test

Not all theory test questions are created equal. Some have failure rates above 50% — meaning most people get them wrong. The reason? They test counter-intuitive facts that feel wrong even when they're right, or they use careful wording designed to catch people who skim-read.

Here are the 20 most commonly failed questions, grouped by category, with explanations of why each one catches people out.

1. "What does a broken yellow line along the kerb mean?" — It means no parking during business hours. Most people think it means no parking at any time (that's a double yellow line).
2. "What does a white diamond road marking mean?" — It indicates you're approaching a pedestrian crossing. Frequently confused with other approach markings.
3. "What does a continuous white line in the centre of the road mean?" — You must not cross or straddle it. People assume broken=no and continuous=yes, when it's the opposite.
4. "What does an amber traffic light mean?" — Stop if you can safely do so. NOT "speed up" and NOT "proceed with caution" — those are the trap answers.
5. "What does a regulatory sign with a red circle and diagonal line mean?" — Prohibition of the action shown inside. People confuse prohibition with mandatory signs (blue circles).

6. "Who has right of way at an unmarked crossroads?" — Nobody has automatic right of way. This is the most commonly failed question. People assume the car going straight or the car on the right has priority, but at an unmarked junction, you must approach with extreme caution and be prepared to yield.
7. "When can you overtake on the left?" — When the vehicle in front is turning right and you can pass safely on the left, or in slow-moving lanes of traffic. People either think "never" or "always in heavy traffic".
8. "What is the speed limit on a national road?" — 100 km/h (single carriageway) or 120 km/h (motorway). People confuse these two, or guess 80 km/h.
9. "When must you use dipped headlights?" — At night on lit roads, in built-up areas, when meeting oncoming traffic, in fog/rain/snow. The common mistake is thinking full beam is always correct at night.
10. "What should you do if an ambulance is approaching with sirens?" — Pull over to the left and stop if necessary. Do NOT speed up, stop suddenly in the middle of the road, or mount the footpath.

11. "What is the minimum legal tyre tread depth?" — 1.6mm across the central three-quarters of the tyre. The most guessed answers are 1mm and 2mm.
12. "What is the blood alcohol limit for learner drivers?" — 20mg per 100ml of blood. Full licence holders have a 50mg limit. Learner and professional drivers have the stricter 20mg limit.
13. "How often must a car over 4 years old have an NCT?" — Every 2 years (cars 4-9 years old) or every year (10+ years). People think it's every year from year 4.
14. "What penalty points result in disqualification for a learner driver?" — 7 penalty points (compared to 12 for full licence holders).
15. "What document must you carry while driving?" — Your driving licence or learner permit. You're not legally required to carry insurance or NCT cert while driving, though Gardaí can request to see them within 10 days.

16. "What should you do if your car starts to aquaplane?" — Ease off the accelerator gently without braking. Do not brake suddenly or steer sharply. People instinctively think "brake" but this makes it worse.
17. "What safe distance should you keep from the car in front?" — At least 2 seconds in dry conditions, 4 seconds in wet conditions. People say "one car length" which is dangerously insufficient at speed.
18. "What should you do at the scene of an accident?" — Secure the area, call 112/999, do NOT move injured people unless there's immediate danger from fire or explosion. Moving injured people is the trap answer.
19. "When should you NOT use your horn?" — Between 11:30pm and 7am in a built-up area (unless there's an emergency). Most people don't know the specific hours.
20. "What is the safe passing distance for a cyclist?" — At least 1 metre at speeds below 50 km/h, and 1.5 metres at higher speeds. This was updated in recent years and catches people who studied with older material.

• Flag and review — Every time you get one of these wrong in practice, bookmark it. Come back tomorrow. Spaced repetition is the single most effective learning technique.
• Read ALL four options — The wrong answers are designed to sound right. Often two answers are very similar, with one being slightly more correct.
• Watch for absolute words — "Always", "never", "only", "must" — these words change everything. If an answer says "always" and there are exceptions, it's wrong.
• Learn the numbers — 1.6mm tread depth, 20mg BAC for learners, 50mg for full licence, 2-second rule, 7 penalty points for disqualification. These are facts, not opinions — memorise them.