Bahrain Heavy Vehicle Theory key terms

The maximum total weight a vehicle is designed to carry, including the vehicle itself, fuel, driver, passengers and cargo, as set by the manufacturer and shown on the vehicle plate.

The weight of cargo, passengers and any other load a vehicle may legally carry, calculated by subtracting the vehicle's kerb weight from its permitted gross weight.

The maximum weight permitted on a single axle or axle group, set by law and by tyre and suspension design, so that road surfaces and components are not overloaded.

The way cargo weight is spread across axles and along the vehicle so that each axle stays within its limit and handling, braking and steering remain stable.

The point where the total weight of a vehicle and its load is considered to act; a high or rearward point increases rollover risk and reduces steering grip.

The use of straps, chains, lashings or restraints to stop cargo shifting, sliding or falling during normal driving, braking and emergency manoeuvres.

The maximum force a strap, chain or other securing device is rated to withstand in service, marked on the device and used to work out how many are needed.

The horseshoe-shaped plate on a tractor unit that locks onto the trailer kingpin, allowing the trailer to pivot and transmitting towing and braking forces.

The vertical pin under the front of a semi-trailer that locks into the tractor's fifth wheel, joining the two vehicles and carrying pulling and braking loads.

Retractable supports under the front of a semi-trailer that hold it upright when uncoupled; they must be fully raised before the vehicle is driven away.

A braking system powered by compressed air, where pressure releases the spring brakes and applies the service brakes, giving strong, repeatable braking on heavy vehicles.

A parking and emergency brake that uses a powerful spring to apply the brake when air pressure is lost, so the vehicle fails safe rather than rolling freely.

A buzzer and light that alerts the driver when reservoir pressure falls too low to brake safely, signalling that the vehicle must be stopped and the fault investigated.

A device that slows the vehicle using engine compression or a retarder rather than the wheel brakes, helping control speed on long descents without brake fade.

Loss of braking power caused by overheating of brake drums, discs or linings after repeated or prolonged use, often on long downhill runs with a loaded vehicle.

Local rules that ban or limit the use of compression-release engine brakes in certain areas, usually to reduce noise, and must be obeyed by drivers using them.

A recording device fitted to heavy vehicles that logs driving time, other work, breaks and rest, providing evidence of compliance with hours rules.

The legal limits on how long a driver may drive before taking a break and within a working day or week, set to reduce fatigue-related crashes.

The minimum uninterrupted rest a driver must take in each 24-hour period before starting the next duty, allowing recovery from the previous day's work.

Physical and mental tiredness that slows reactions and judgement; it is a major crash cause and must be managed with proper rest, breaks and sleep.

The required procedure for recording and reporting any vehicle fault found during checks, so it is repaired or the vehicle is taken out of service.

A systematic check of tyres, brakes, lights, fluids, couplings and load before setting off, intended to catch faults that could cause a breakdown or crash.

A physical circuit of the vehicle and trailer looking and listening for damage, loose items, air leaks and insecure loads before and during a journey.

The height of the rubber blocks on a tyre, which must stay above the legal minimum to maintain grip, especially in wet conditions and under heavy loads.

The gap kept behind the vehicle ahead, allowing time to react and stop; it must grow with speed, load and poor weather or visibility.

The distance a vehicle travels from the moment the brakes are applied until it stops, increasing greatly with speed, weight, wet roads and worn brakes.

An area around a heavy vehicle that the driver cannot see in mirrors, where other road users may be hidden, especially close alongside or behind a trailer.

The skill of spotting developing risks early, such as a pedestrian stepping out or a vehicle emerging from a side road, and planning a safe response.

The rule that decides which road user gives way at a junction, based on signs, markings and the general rule of yielding to traffic already on the main road.

Painted lines, arrows, boxes and edge markings on the road surface that guide, warn and regulate traffic, and must be read together with signs and signals.

The convention for entering, circulating and leaving a roundabout, including giving way to traffic already on the circle and signalling intent clearly.

The amount of alcohol in the blood, measured in milligrams per 100 millilitres; driving above the legal limit is an offence with severe penalties.

Any condition that reduces a driver's ability to control a vehicle safely, including alcohol, drugs, illness, fatigue or medication side effects.

The driver's legal and personal duty to be well enough, rested enough and free of impairing substances to operate a heavy vehicle safely on each trip.

The steps taken at a crash scene to protect casualties and other traffic, such as warning triangles, hazard lights and keeping clear of moving vehicles.

The order of action at an incident: check the scene is safe, assess response and breathing, call emergency services, then control bleeding and keep casualties warm.

Driving techniques such as smooth acceleration, early gear changes, steady speed and avoiding unnecessary idling that cut fuel use, emissions and running costs.

Switching off the engine when stationary for more than a short period, saving fuel, reducing emissions and noise, and lowering engine wear.

The authorisation an operator needs to run heavy goods vehicles, requiring suitable maintenance arrangements, a transport manager and financial standing.

The class of licence that permits a driver to operate a particular weight and type of vehicle, such as rigid truck, articulated combination or bus.