DTT HGV Motorway Driving and CPC Requirements 4 — Questions and Answers
Question 1: How do weather conditions affect the safe speed for a truck on a motorway?
- In adverse weather, the safe speed is much lower than the speed limiter setting — the driver must always drive to the conditions (Correct answer)
- Speed limiters set the maximum safe speed in all conditions — no reduction needed if within the limit
- Only ice requires speed reduction — rain does not affect a truck's stopping ability significantly
- Reducing speed in poor weather is only necessary when the motorway speed limit signs instruct it
Correct answer: In adverse weather, the safe speed is much lower than the speed limiter setting — the driver must always drive to the conditions
The speed limiter sets a maximum — not a safe speed in all conditions. In rain, fog, ice, or strong winds, the safe speed may be well below 90 km/h. Driving at the limiter's maximum in poor conditions is a serious offence.
Question 2: What is the 'blind spot' problem specific to trucks and buses, and how should drivers manage it?
- Large vehicles have much larger blind spots than cars — especially nearside, behind, and in front. Drivers must use mirrors, cameras, and physical checks to manage these areas (Correct answer)
- Modern trucks have no blind spots if fitted with blind spot cameras
- Blind spots only apply when reversing — forward driving has full visibility
- Trucks have smaller blind spots than cars due to being taller
Correct answer: Large vehicles have much larger blind spots than cars — especially nearside, behind, and in front. Drivers must use mirrors, cameras, and physical checks to manage these areas
Trucks and buses have very large blind spots — especially on the nearside (left), directly behind, and immediately in front of the cab. Cyclists and pedestrians can be invisible in these zones. Regular mirror scanning and nearside cameras are essential.
Question 3: What does 'vehicle stability control' (ESP/ESC) do on a heavy vehicle?
- Detects impending rollover or loss of lateral stability and automatically reduces engine torque and applies individual wheel brakes to stabilise the vehicle (Correct answer)
- Controls the vehicle's suspension stiffness during cornering
- Monitors tyre pressure and adjusts speed automatically
- Prevents wheel spin during acceleration on slippery surfaces only
Correct answer: Detects impending rollover or loss of lateral stability and automatically reduces engine torque and applies individual wheel brakes to stabilise the vehicle
Electronic Stability Programme (ESP) / Electronic Stability Control (ESC) detects when the vehicle is about to roll or go into a skid and intervenes automatically — reducing engine torque and selectively applying brakes to correct the trajectory.
Question 4: What is the purpose of the 'Advanced Emergency Braking System' (AEBS) on trucks?
- AEBS automatically detects vehicles or obstacles ahead and applies emergency braking if the driver does not respond — preventing or mitigating rear-end collisions (Correct answer)
- AEBS applies maximum braking when the driver presses the brake pedal regardless of road conditions
- AEBS is a driver-assist that warns of hazards but does not apply brakes automatically
- AEBS applies the trailer brakes only in an emergency
Correct answer: AEBS automatically detects vehicles or obstacles ahead and applies emergency braking if the driver does not respond — preventing or mitigating rear-end collisions
AEBS (mandatory on new trucks since 2015) uses radar and cameras to detect forward collision risk. It first warns the driver, then if no response, automatically applies emergency braking to prevent or reduce the severity of a collision.
Question 5: What is the importance of route planning for a heavy vehicle operator?
- Identifying low bridges, weight-restricted roads, unsuitable road widths, and hazardous bends before departure prevents incidents and prohibitions (Correct answer)
- Route planning is only necessary for loads over 44 tonnes
- GPS systems handle all route planning — drivers do not need to plan routes manually
- Route planning is the logistics manager's responsibility — not the driver's concern
Correct answer: Identifying low bridges, weight-restricted roads, unsuitable road widths, and hazardous bends before departure prevents incidents and prohibitions
Route planning is essential for heavy vehicles — low bridges cause catastrophic impacts, weight-restricted roads carry prosecution risk, and some roads are physically impassable. Both operators and drivers share responsibility.
Question 6: What is the rule about overtaking other trucks on a two-lane motorway in Ireland?
- Permitted using lane 2 — but be aware of the long time needed to complete the overtake and the risk of frustrating faster traffic (Correct answer)
- Trucks must never overtake other trucks on a motorway
- Trucks may only overtake on motorways if the speed difference is at least 20 km/h
- Truck-to-truck overtaking is restricted to off-peak hours only
Correct answer: Permitted using lane 2 — but be aware of the long time needed to complete the overtake and the risk of frustrating faster traffic
Trucks may overtake on a two-lane motorway using lane 2. However, a truck taking a long time to overtake another truck travelling at similar speed creates hazards for faster following traffic. Overtake only when there is a genuine speed difference.
DTT HGV Motorway Driving and CPC Requirements 4
How do weather conditions affect the safe speed for a truck on a motorway?