DTT HGV Cheat Sheet 2026

The 30 highest-yield DTT HGV facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. The landing legs of a semi-trailer must be fully raised: → Before the vehicle combination moves off
2. Before reversing a tractor unit under a semi-trailer for coupling, the fifth wheel should be: → Clean, greased and in the unlocked (open) position
3. What happens to tachograph data if a driver removes their card from the digital unit mid-shift? → The vehicle's internal memory continues recording all data — it is not lost
4. What are chevron signs (black and white arrows on a curve) designed to indicate? → The direction and severity of a sharp bend — they guide drivers through the curve
5. Which authority is primarily responsible for enforcing tachograph regulations in Ireland? → An Garda Síochána and the Road Safety Authority (RSA)
6. At what point should you stop reversing the tractor unit when coupling to a trailer? → When you hear or feel the fifth wheel jaws lock onto the kingpin
7. What does a sign showing an axle weight limit (e.g., '8t' with an axle symbol) mean? → No vehicle with any axle weight exceeding the stated limit may use this road
8. What equipment can be used to check if a commercial vehicle is overloaded? → A weighbridge or portable axle weigh pads
9. After how many hours of continuous driving must a driver take a break? → After 4.5 hours of driving — a break of at least 45 minutes is required
10. What is a 'fifth wheel' coupling on a heavy goods vehicle? → The coupling device on the tractor that locks onto the trailer kingpin
11. What does the tachograph record when the vehicle is stationary but the engine is running? → Other work or availability time — depending on which mode the driver selects
12. What is the maximum weight permitted on a tandem axle (two axles in a bogie) with air suspension? → 20,000 kg for a driven tandem axle with air suspension
13. A driver is asked by a Garda to produce tachograph records. What records must they be able to show? → Current day's record plus the last 28 days of records on the driver card
14. At what distance should a warning triangle be placed behind a broken-down truck on a single carriageway? → At least 45 metres behind the vehicle on the same side of the road
15. What is the 'fortnightly rule' in EU driver hours regulations? → In any two consecutive weeks, total driving must not exceed 90 hours
16. What is the maximum permissible weight on a single driven axle in Ireland? → 11,500 kg
17. Under EU Regulation 561/2006, what is the maximum continuous driving time before a break is required? → 4 hours 30 minutes
18. The kingpin on a semi-trailer connects with which part of the tractor unit? → The fifth wheel coupling plate
19. When must the 45-hour weekly rest begin? → Within 6 consecutive days from the end of the previous weekly rest period
20. The yellow (service) airline on a truck-trailer combination is used for: → Controlling the service (foot) brakes on the trailer
21. A driver starts a daily rest at 18:00. When is the earliest they can resume driving under a regular 11-hour daily rest? → 05:00 the following morning (18:00 + 11 hours)
22. How long must an employer retain digital tachograph data downloaded from the vehicle unit? → At least 12 months from the date the data was recorded
23. If you discover a cracked or damaged kingpin during a pre-coupling inspection, you should: → Not couple the trailer until the kingpin has been repaired or replaced
24. What is the maximum permitted weight for a tri-axle group (three axles in a bogie)? → 24,000 kg
25. What does 'driving time' mean under EU tachograph regulations? → The duration of the driving period as recorded automatically when the vehicle is in motion
26. The red (emergency) airline on a truck-trailer combination controls: → The spring (parking/emergency) brakes on the trailer
27. What must a driver do with their analogue tachograph charts after completing a journey? → Keep them for 28 days and produce them on demand by enforcement authorities
28. What is the maximum permissible gross vehicle weight for a rigid two-axle truck in Ireland? → 18,000 kg (18 tonnes)
29. After coupling a trailer, how should you test that the coupling is secure? → Attempt to move forward with the trailer parking brake applied
30. What does 'bobtail' mean in the context of truck driving? → Driving a tractor unit without a trailer attached