DRTS Heavy-Vehicle Theory flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Chain of responsibility

A legal framework placing duties on parties who consign, pack, load, drive and receive goods to prevent breaches of mass, dimension, load restraint, speed and fatigue rules.

Heavy-vehicle speed limit

A posted limit that may be lower for heavy vehicles than for cars on the same road; the lower sign always governs the heavy vehicle.

Follow-distance rule

A common heavy-vehicle guideline of at least four seconds behind the vehicle ahead at highway speed, increased in rain, darkness or when fully loaded.

Licence class requirement

The driver's licence class must cover the vehicle's gross vehicle mass or the combination's gross combination mass before the vehicle may be driven.

Oversize load warning

Loads projecting beyond dimension limits require flags, lights, pilot vehicles or permits as specified by the jurisdiction and any permit conditions.

Pre-start walk-around

A check of tyres, wheel nuts, lights, air pressure, brake adjustment, fluid leaks, load security and coupling security before the vehicle is driven.

Air-brake leak test

With the engine off and system charged, a pressure drop above about 2 psi per minute for a single vehicle or 3 psi for a combination indicates a leak.

Brake adjustment limit

A pushrod stroke beyond the manufacturer's limit means the brake is out of adjustment and the vehicle is unroadworthy until repaired.

Defect categories

Minor defects may be recorded and repaired at the next service; major defects require repair before use; dangerous defects require immediate removal from service.

Defect reporting duty

A driver who becomes aware of a defect must report it to the operator and record it; the operator must act on the report and keep records.

Higher mass limits

HML access requires compliant suspension, road-friendly tyres and enrolment in an approved scheme, and cannot be used on roads not approved for it.

Gross combination mass

The GCM must not exceed the lesser of the vehicle's rated GCM and the applicable legal combination limit for the road and configuration.

Load restraint requirement

The load must be restrained so it will not shift under braking, acceleration, cornering or vibration, and the restraint system must be rated for the load mass.

Axle group load sharing

Poor load distribution can overload one axle while total mass is legal; weighbridge checks measure per-axle and per-group loads, not just total.

Fatigue work time

Work time includes driving plus all other tasks for the operator such as loading, inspections and paperwork; rest must be continuous and free of duties.

Minimum rest break

A common fatigue rule requires a minimum continuous rest break, such as 30 minutes, after a set period of work such as 5 to 5.5 hours.

Work diary accuracy

A work diary or electronic work diary must record work and rest accurately; false entries are an offence and can void a fatigue compliance defence.

Fatigue warning signs

Micro-sleeps, lane drift, yawning and difficulty focusing indicate fatigue even within legal hours; the driver must stop and rest.

Spring brake operation

The spring brake is held off by air pressure; a loss of air pressure causes the spring brakes to apply automatically as a fail-safe parking brake.

Governor cut-out pressure

Compressor cut-out is typically around 100 to 120 psi and cut-in around 85 psi; pressure below the warning threshold triggers a low-pressure alarm.

Brake fade

Repeated heavy braking overheats drums and reduces friction; use engine braking and a lower gear on long descents rather than continuous service braking.

Trailer supply line

The trailer's emergency supply line must be connected and charged before the trailer brakes release; a broken supply line applies the trailer spring brakes.

Centre of gravity height

Raising the CoG by loading high increases rollover risk; the rollover threshold is roughly the track width divided by twice the CoG height.

Rearward load bias

A rearward load bias reduces steer-axle load and can cause understeer or loss of steering grip, especially on low-friction surfaces.

Off-tracking

The rear wheels of a long vehicle track inside the front wheels in a turn; the longer the wheelbase, the greater the swept path.

Kinetic energy and speed

Braking distance increases with mass, and kinetic energy rises with the square of speed, so doubling speed roughly quadruples the energy to dissipate.

Downhill speed control

Select a gear that holds a safe speed without continuous service braking, and use engine or retarder braking to avoid brake fade.

Scan pattern

Look well ahead about 12 to 15 seconds of travel, check mirrors every few seconds, and monitor blind spots on both sides of the vehicle.

Heavy-vehicle blind spots

Large blind areas exist directly in front, behind and alongside a heavy vehicle; a passing vehicle may be invisible even when mirrors are checked.

Condition-based speed

Drive to visibility, road surface, load and traffic rather than the posted limit; the posted limit is a maximum, not a target.

Post-crash duties

Stop, secure the scene, check for injuries, call emergency services and exchange details; do not leave the scene unless legally permitted.

Incident evidence preservation

Do not alter the scene, vehicle or records after a serious incident until authorised; work diaries, telematics and maintenance records may be required.