Mixed Deck — All DTT HGV Topics Flashcards

A driver starts a daily rest at 18:00. When is the earliest they can resume driving under a regular 11-hour daily rest?

Answer: 05:00 the following morning (18:00 + 11 hours)

Regular daily rest is 11 consecutive hours. Starting rest at 18:00 means the earliest resume time is 05:00 (18:00 + 11 hours). The driver may not start driving before this time.

How does the air brake system maintain pressure during a long journey?

Answer: An engine-driven compressor continuously tops up the air reservoirs as air is used during braking

An air compressor driven by the engine continuously replenishes the air reservoirs. A governor valve stops the compressor when maximum pressure is reached and restarts it when pressure drops — maintaining consistent operating pressure.

What is the importance of pre-journey route checks for hazardous roads or bridges for a truck driver?

Answer: A bridge collapse or getting stuck under a low bridge can be fatal and career-ending — route checks prevent costly and dangerous incidents

Pre-journey route checks are essential. Low bridges (under 4.65m) cause catastrophic and sometimes fatal collisions. Weight-restricted bridges can collapse or lead to prohibition. GPS maps are not always current with restrictions.

What CPC training topic directly reduces fuel costs for a transport operator?

Answer: Eco-driving and fuel-efficient driving techniques — proven to reduce fuel consumption by 10-15%

Eco-driving training is directly linked to fuel savings. Studies consistently show 10-15% fuel reduction when drivers apply eco-driving principles — a significant saving given that fuel is one of the largest transport operating costs.

What must a truck or bus driver do before joining a motorway from a slip road?

Answer: Accelerate to match motorway traffic speed on the slip road, check mirrors and blind spots, and merge safely into a gap in the left lane

Use the full length of the slip road to reach motorway speed, carry out MSM routine (mirrors, signal, manoeuvre), check the blind spot, and merge smoothly into a gap. Merging slowly disrupts motorway traffic and is dangerous.

What is the maximum gross vehicle weight (GVW) for a standard rigid truck on Irish roads?

Answer: 32 tonnes for a two-axle rigid (higher for multi-axle combinations up to 44 tonnes for articulated)

Weight limits depend on axle configuration. A two-axle rigid truck is limited to 18 tonnes. Articulated vehicles with 5 or more axles can reach 44 tonnes. The standard 6-axle artic limit is 44 tonnes.

What does 'bobtail' mean in the context of truck driving?

Answer: Driving a tractor unit without a trailer attached

A 'bobtail' tractor is a tractor unit being driven without a trailer; this condition affects braking distance and handling due to the different weight distribution.

What must a driver check regarding the trailer air lines (susie hoses) before moving off?

Answer: That both red (emergency) and yellow (service) airlines are correctly coupled, undamaged, and secure — not dragging on the ground

Both the red (emergency/supply) and yellow (service/brake) airlines must be correctly connected to the trailer, not damaged or kinked, and positioned so they do not drag or snag when turning.

What does a sign showing a width restriction (e.g., '2.5m' with width indicator arrows) mean?

Answer: The road or structure ahead has a width restriction — vehicles wider than the stated measurement cannot pass

Width restriction signs indicate that the road, bridge, or structure ahead cannot accommodate vehicles wider than the stated measurement. Drivers must know their vehicle's width including mirrors and any wide loads.

What is 'jackknifing' and how can a truck driver prevent it?

Answer: The trailer pivots around the fifth wheel creating a V-shape — prevented by gradual braking, avoiding over-braking the tractor while trailer brakes lock

Jackknifing occurs when the trailer's braking locks the trailer wheels causing it to swing outward while the tractor continues forward. Prevent by using progressive braking, avoiding over-braking on slippery surfaces.

What is the primary purpose of a tachograph in a commercial vehicle?

Answer: To record driving time, rest periods, and vehicle speed to ensure compliance with EU driver hours regulations

A tachograph is a scientific instrument fitted to commercial vehicles to record driving time, rest periods, other work periods, and vehicle speed — ensuring compliance with EU Regulation 561/2006 on driver hours.

What is the maximum permitted overhang of a load beyond the rear of a vehicle in Ireland?

Answer: Up to 2 metres — beyond 1 metre, a rear marker board is required; beyond 2 metres, a police escort may be needed

Loads may overhang up to 2 metres beyond the rear without special permits in most cases, but rear overhang beyond 1 metre requires a marker board. Longer overhangs require abnormal load permits.

How should a truck driver check the coupling between a tractor unit and trailer?

Answer: Check the fifth-wheel lock engagement, safety catch is secured, trailer kingpin seated correctly, and perform a 'pull-test' by moving forward gently against the brakes

Coupling check: confirm the kingpin is locked in the fifth wheel, the safety catch is engaged, airlines and electrical connections are correctly made, and perform a pull-test with the trailer brakes applied to confirm lock.

If your truck catches fire while driving, what should you do?

Answer: Pull over safely, turn off the engine, evacuate the cab, use a fire extinguisher on a small fire if safe to do so, and call the fire brigade

Stop the vehicle safely, turn off the engine to cut fuel supply, evacuate immediately, and move away from the vehicle. Only attempt to fight a small fire if you have the correct extinguisher and it is safe to do so. Call 999/112 for the fire brigade.

How does overloading affect a vehicle's braking performance?

Answer: Braking distances increase significantly as the brakes must absorb more kinetic energy, and brakes may overheat and fade

An overloaded vehicle has more momentum and kinetic energy, requiring greater braking force and longer distances to stop. Brakes can overheat under the additional strain, leading to brake fade. Overloading also affects steering and vehicle stability.

What is the maximum driving time in any two consecutive weeks?

Answer: 90 hours over two consecutive weeks

Even though a driver can drive up to 56 hours in one week, the total for any two consecutive weeks must not exceed 90 hours. This prevents every week being a maximum week.

At what point should you stop reversing the tractor unit when coupling to a trailer?

Answer: When you hear or feel the fifth wheel jaws lock onto the kingpin

The audible click and physical resistance indicate that the fifth wheel jaws have engaged and locked around the kingpin, confirming a successful coupling.

What is the tyre tread depth minimum for a commercial vehicle (truck or bus)?

Answer: At least 1mm across 75% of the tread width and around the full circumference

Commercial vehicles (trucks and buses) require a minimum tread depth of 1mm across at least 75% of the tread width and around the entire circumference of the tyre.

What does 'compensatory rest' mean in the context of EU driver hours?

Answer: Additional rest required to offset a previous reduction in weekly rest — must be attached to a daily or weekly rest period within 3 weeks

Compensatory rest is the additional rest required when a driver has taken a reduced weekly rest. The reduction amount must be added to a subsequent daily or weekly rest within the third week following the reduction week.

What is the correct response when a tyre blows out on a truck travelling on a motorway?

Answer: Grip the steering firmly, ease off the throttle gradually, do not brake sharply, steer to the hard shoulder, and stop safely

A tyre blowout on a heavy vehicle at speed causes a sudden pull toward the affected side. Resist braking immediately — firm wheel grip and gradual deceleration gives the best chance of maintaining control while pulling over.