DTT HGV Practice Test

DTT HGV Exam at a Glance

Facts verified Oct 25, 2026 against Road Safety Authority. Dates that have passed are removed automatically.

DTT HGV Study Tips

• Create a structured study schedule at least 4-6 weeks before your DTT HGV exam date.
• Focus on understanding core concepts rather than memorising answers for the Irish Driver Theory Test for Trucks and Buses.
• Use our free practice tests to identify weak areas and track your progress over time.
• Review the official DTT HGV exam syllabus to ensure complete topic coverage.
• Take timed practice sessions to build your exam pace and reduce test-day anxiety.

Free Irish DTT Truck/Bus Study Tools

Interactive Irish DTT Truck/Bus resources on PracticeTestGeeks, free to start:

• DTT HGV Coupling and Uncoupling Trailers 1 — 7 questions with answer explanations
• Irish DTT Truck/Bus flashcards — review key terms and concepts card by card
• Irish DTT Truck/Bus study guide — topic-by-topic overview of what the exam covers
• Irish DTT Truck/Bus cheat sheet — one-page printable summary for last-minute review

According to Road Safety Authority, “A full current Category B Irish Driving Licence (or one from an EU/EEA member state or Switzerland or Ukraine)”^[2]

Worked examples: how to reason through DTT HGV questions

These are practice questions written for this site, not questions from the real exam. Each explanation shows why the right answer is right and why the others are wrong.

Example 1

Question: What should a driver check regarding the braking system during a pre-trip inspection?

1. Air brake reservoir pressure, brake warning lights, and test the foot and hand brakes before moving
2. Only check that the brake pedal feels firm
3. Brakes are checked only during CVRT and monthly service
4. Check brake fluid level only

Answer: A. Air brake reservoir pressure, brake warning lights, and test the foot and hand brakes before moving

Explanation:

The correct answer is the one that covers the whole braking system before you move. On an air-braked vehicle you check that reservoir pressure builds, that the warning lights go out as it should, and that the foot and hand brakes both work. That is why the first option is right.

Checking only that the pedal feels firm is wrong because it says nothing about air pressure or the parking brake. Saying brakes are checked only at CVRT and in a monthly service is wrong because the driver is responsible for a check every trip. Checking brake fluid alone is wrong because it suits hydraulic systems and misses the air system.

Rule to remember: the driver inspects the brakes before every trip, and tests them, not just looks at them.

Example 2

Question: What is the air pressure threshold at which the low-pressure warning alarm activates in an air brake system?

1. Typically around 4.5-5.5 bar — the alarm warns the driver before the pressure drops to spring brake activation level (around 2.5 bar)
2. When the pressure drops to zero
3. Only when the brakes are physically failing to respond
4. At 7 bar — the maximum pressure of the system

Answer: A. Typically around 4.5-5.5 bar — the alarm warns the driver before the pressure drops to spring brake activation level (around 2.5 bar)

Explanation:

The correct answer is that the low-pressure alarm sounds at roughly 4.5-5.5 bar, which is above the level of about 2.5 bar where the spring brakes apply. The alarm is an early warning, so you get time to stop safely before the brakes apply on their own.

Zero is wrong because by then there would be no warning at all and the vehicle would already be braked. The option about brakes physically failing to respond is wrong because the alarm is triggered by pressure, not by how the vehicle behaves. 7 bar is wrong because that is the top of the system's range, and an alarm there would sound all the time.

Rule to remember: the warning comes well before the spring brakes, so act on it straight away and pull over.

Example 3

Question: What is the function of load sensing valves in an air brake system?

1. They adjust the braking force to the axle based on the load carried — preventing wheel lock on lightly loaded axles
2. They control maximum air pressure in the reservoir
3. They prevent over-braking on the steering axle
4. They monitor tyre pressure and adjust brake force accordingly

Answer: A. They adjust the braking force to the axle based on the load carried — preventing wheel lock on lightly loaded axles

Explanation:

The correct answer is that a load sensing valve adjusts braking force to an axle according to the load carried. It reads suspension compression as a sign of load, so a lightly loaded axle gets less braking force and is less likely to lock its wheels.

Controlling maximum reservoir pressure is wrong because that job belongs to the governor, not this valve. Preventing over-braking on the steering axle is wrong because the valve works on the rear axles, not the steering axle. Monitoring tyre pressure is wrong because the valve does not measure tyres at all.

Rule to remember: an empty or part-loaded vehicle needs less braking force at the rear, and load sensing is how the system provides it.

How to use these practice tests

Start with the free DTT HGV practice test to see which topics you already know and which you do not. Write down the topics you miss, then work through the matching topic sets rather than repeating the general test.

Spend most of your time on the technical areas, since they take the longest to learn. Try Passenger Safety and Air Brakes, Tachograph Rules and Drivers Hours, then Driver Hours and EU Regulations. After that, cover the practical topics: Load Security, Vehicle Weights and Vehicle Inspection and Load Securing.

When you get a question wrong, read the explanation, then check the rule in the official Road Safety Authority material. Our questions are written by us and are not real exam questions, so use them to find gaps, not to predict the paper.

Near test day, sit the practice test in one go and keep to the time limit for the test you booked. Finish with Road Signs and Emergency Procedures to tidy up weak spots.

Ready to Pass the DTT HGV?

Join thousands of candidates who have used our free practice tests to prepare for the Irish Driver Theory Test for Trucks and Buses. Start practising today and build the confidence you need to succeed. Practice with the free Irish DTT Truck/Bus practice test on PracticeTestGeeks (7 questions with answer explanations).

Sample Irish DTT Truck/Bus Practice Questions

Try these questions from our free Irish DTT Truck/Bus practice tests. The correct answer and an explanation follow each question.

1. What is the significance of 'high-sided vehicle' warnings on motorway gantry signs?

   • A. Strong crosswinds make high-sided vehicles vulnerable to overturning — reduce speed significantly and grip the wheel firmly in exposed sections
   • B. High-sided vehicle warnings apply only to vehicles over 4.5 metres tall
   • C. The warning is advisory only — modern trucks are stable in crosswinds
   • D. High-sided warnings are for cars sharing the road with trucks — not for the trucks themselves

Answer: A. Strong crosswinds make high-sided vehicles vulnerable to overturning — reduce speed significantly and grip the wheel firmly in exposed sections

High-sided vehicles (trucks, buses, curtainsiders, box trailers) present a large surface area to crosswinds. Strong lateral wind forces can cause rollover, especially on bridges and open exposed sections of motorway.

Answer: A. No vehicle with any axle weight exceeding the stated limit may use this road

An axle weight limit sign restricts individual axle weights, not total vehicle weight. This is different from a gross weight limit. A vehicle might be within the total weight limit but still exceed the axle weight limit, especially if poorly loaded.

Answer: A. Charts must be retained for 28 days and available for inspection during that period

Drivers must keep analogue charts and digital card printouts for the current week plus the last chart/printout from the previous week — totalling up to 28 days — and produce them on request by enforcement authorities.

Answer: A. EBS integrates ABS, traction control, stability control, and optimised brake force distribution electronically — improving safety and brake efficiency

EBS (Electronic Braking System) uses electronic control to optimise brake force distribution across axles, integrating ABS, traction control, and stability systems. It improves braking performance and reduces stopping distances.

Take the full Irish DTT Truck/Bus practice test