Cambodia Heavy Vehicle Driving Test key terms

The maximum total weight a vehicle is designed and legally permitted to carry, including the vehicle itself, fuel, passengers and cargo. Overloading beyond GVM is an offence and reduces braking and stability.

The weight of cargo and passengers a vehicle may carry, calculated by subtracting the vehicle's kerb weight from its gross vehicle mass. Exceeding payload is a common cause of overload fines and brake failure.

The portion of a vehicle's total weight carried by one axle or axle group. Each axle has a rated limit, and uneven or excessive loading can overload an axle even when total weight is legal.

The way cargo weight is spread over the vehicle's axles and bed. Correct distribution keeps steering axles loaded, prevents axle overload, and maintains braking balance and cornering stability.

The point where the vehicle's total weight effectively acts. A high or shifted centre of gravity, caused by tall or badly placed loads, increases rollover risk in turns and sudden manoeuvres.

The use of straps, chains, binders, tarpaulins or side gates to stop cargo shifting, sliding or falling. Insecure loads endanger other road users and are a legal offence.

The maximum force a strap, chain or rope is rated to withstand when securing a load. Using lashings below the required capacity can allow cargo to break free under braking or cornering.

A systematic check of tyres, brakes, lights, fluids, mirrors, couplings and load before starting a journey. It catches defects early and is a legal duty for heavy vehicle drivers.

A quick visual and physical inspection around the vehicle at the start of each shift, looking for tyre damage, leaks, loose parts, broken lights and load problems before driving.

A written record notifying the operator of any fault found on the vehicle that affects safety or compliance. Drivers must report defects and must not drive a vehicle with a major safety defect.

The condition of a vehicle being safe and legal to use on the road, with working brakes, lights, steering, tyres and emissions equipment. Regular inspection and maintenance keep a vehicle roadworthy.

A check of the air brake system for pressure build-up, leakage and correct low-pressure warning operation. It confirms the brakes will hold and stop the vehicle safely.

Loss of braking power when brakes overheat, usually from repeated or prolonged use on long descents. The pedal or lever feels weak and stopping distance increases sharply.

Using a low gear so the engine's compression resists the vehicle's motion, slowing it without continuous service brake use. It helps control speed on long downhill grades and reduces brake fade.

An auxiliary slowing device, such as an exhaust brake or hydraulic retarder, that reduces speed without wearing the service brakes. It is used to hold a safe speed on long descents.

A fail-safe parking brake that uses a strong spring to apply the brakes when air pressure is lost. It engages automatically if system pressure drops too low, stopping the vehicle.

The total distance travelled from the moment a hazard is seen until the vehicle stops, including reaction distance and braking distance. It grows with speed, load and wet or poor road surfaces.

The gap kept between your vehicle and the one ahead. Heavy vehicles need a larger gap than cars because of greater mass and longer stopping distances, especially when loaded.

The delay between noticing a hazard and beginning to brake or steer. Fatigue, alcohol, distraction and illness lengthen reaction time, increasing the distance covered before slowing.

An area around the vehicle that cannot be seen in the mirrors or directly. Heavy vehicles have large blind spots, so drivers must check mirrors and use caution when turning or reversing.

The routine of scanning left and right mirrors and, where fitted, convex and blind-spot mirrors before changing speed, lane or direction. Frequent checks keep other road users in view.

Moving from one traffic lane to another. For heavy vehicles it requires signalling, mirror and blind-spot checks, and enough space because of the vehicle's size and slower acceleration.

When a vehicle tips onto its side or roof, often caused by cornering too fast with a high centre of gravity, sudden steering, or driving onto soft road edges. Rollovers are a leading heavy-truck fatality.

A driving style that anticipates hazards and other people's mistakes, keeps space and time to react, and avoids risky situations. It reduces the chance of a crash regardless of who is at fault.

The skill of spotting developing risks, such as pedestrians, junctions, parked vehicles or changing traffic, early enough to act safely. It improves with scanning and experience.

Managing the vehicle's speed to suit the limit, road conditions, load and visibility. Correct speed control prevents rollovers, brake fade and loss of grip on bends and descents.

The maximum legal speed for a road or vehicle type. Drivers must also reduce speed below the limit when conditions such as rain, darkness or heavy traffic make the limit unsafe.

Choosing the right gear for the load, gradient and road speed. Low gears give more power and engine braking for hills and heavy loads, while high gears suit steady cruising.

A flashing light that signals an intention to turn, change lane or pull out. Signals must be given in good time and cancelled afterwards so other road users are not misled.

A light or device controlling traffic flow, such as red, amber and green lights or a police officer's directions. Drivers must obey signals and stop on red or when directed.

A painted line across the road marking where a vehicle must stop at a junction, signal or sign. Stopping beyond it can obstruct traffic or endanger pedestrians.

Lines, arrows, hatched areas and words painted on the road surface to guide or regulate traffic. Drivers must follow them, including lane arrows and no-overtaking lines.

A circular junction where traffic flows in one direction around a central island. Drivers give way to traffic already on the roundabout and signal clearly when entering and leaving.

To yield priority to other traffic at a junction, roundabout or merging lane. A give-way rule means slowing or stopping if necessary to let others pass safely.

Passing another vehicle travelling in the same direction. For heavy vehicles it needs a clear view, a long safe gap, and attention to no-overtaking markings and the vehicle's slow acceleration.

A person who stands where the driver can see them and gives hand signals to guide a reversing vehicle. The driver stops immediately if the guide is lost from view.

The connection between a towing vehicle and a trailer, such as a fifth wheel or drawbar. It must be locked, checked and secured before driving, or the trailer can separate.

Physical and mental tiredness that slows reactions, reduces attention and increases errors. Drivers must rest, respect driving-hour limits and not drive when drowsy.

The legal limits on how long a driver may drive and work before taking rest breaks. These rules aim to prevent fatigue-related crashes in heavy vehicle operations.

A required period of rest away from driving that lets a driver recover alertness. Breaks must be taken within the legal driving-hour limits and should include sleep where possible.

The amount of alcohol in the blood, measured as a percentage or in grams per litre. Driving above the legal limit is an offence and impairs judgement, reaction and coordination.

The class of driving licence that permits a driver to operate a particular type and weight of vehicle. Driving a vehicle outside your category is unlicensed driving and carries penalties.

The official document authorising a person to drive specified vehicle categories. Drivers must carry it when required and keep it valid, with correct conditions and endorsements.

The official record linking a vehicle to its owner and registration number. A vehicle must be registered and display valid plates and documents to be used on public roads.

Insurance covering injury or damage the driver causes to other people or their property. It is commonly required by law and does not cover the driver's own vehicle.

The steps taken at a crash: securing the scene, warning traffic, calling emergency services, and helping casualties without causing further harm. It protects rescuers and victims.

Immediate basic care given to an injured person before professional help arrives, such as controlling bleeding, keeping the airway open and preventing shock. It can save lives.

A safe side-lying posture for an unconscious but breathing casualty that keeps the airway open and prevents choking. It is used when no spinal injury is suspected.

Contacting police, ambulance or fire services with clear details of location, casualties and hazards. Prompt, accurate calls bring help faster and let responders prepare.