DRTS Heavy-Vehicle Theory cheat sheet

Chain of responsibility (COR) extends primary duty to parties who consign, pack, load, drive, and receive goods; each party must eliminate or minimise fatigue, speed, mass, dimension and load-restraint breaches.

Heavy-vehicle speed limits are posted per jurisdiction and per road class; a posted limit for a truck may be lower than the general car limit on the same road, so the lower sign governs.

Following distance for a heavy vehicle: a common rule is at least 4 seconds behind the vehicle ahead at highway speed, increased in rain, darkness or when fully loaded.

A heavy vehicle must not be driven if the driver's licence class does not cover the vehicle's gross vehicle mass or the combination's gross combination mass.

Loads must not project beyond the vehicle's dimension limits without the required warning devices (flags, lights, pilot vehicles) and any permit conditions.

Low bridges, weight-restricted roads, and tunnel clearances are absolute limits; a driver must not enter a restricted structure without confirmed clearance for the loaded height and mass.

Traffic offences by the driver and by the operator can be prosecuted separately; an operator may be liable even if the driver is not charged.

Emergency vehicles: a heavy vehicle must give way and, where required, stop clear of an intersection until the emergency vehicle has passed.

Pre-start walk-around checks: tyres and pressures, wheel nut indicators, lights and reflectors, air pressure build-up and leak-down, brake adjustment, fluid leaks, load security, and coupling security on combinations.

Air-brake leak test: with the engine off and the system charged, a pressure drop greater than about 2 psi per minute (single vehicle) or 3 psi per minute (combination) indicates a leak requiring attention.

Air pressure build-up: a healthy compressor raises the system from about 85 psi to governor cut-out (typically 100-120 psi) within roughly 3 minutes at fast idle.

Brake adjustment limit: a pushrod stroke beyond the manufacturer's adjustment 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 scheduled service; major defects require repair before the vehicle is used; dangerous defects require immediate removal from service.

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

Tyre minimum tread depth for heavy vehicles is set by jurisdiction (commonly 1.5 mm for cars, higher for heavy tyres), and tyres must be free of cuts, bulges and exposed cords.

Daily inspection records must be retained for the period set by the regulator; missing records are themselves a compliance breach.

General mass limits (GML) vs higher mass limits (HML): HML access requires compliant suspension, road-friendly tyres, and enrolment in an approved scheme; HML cannot be used on roads not approved.

Steer axle limit is commonly around 6 t under GML; drive and trailer group limits depend on the number of tyres and axle spacing, so always check the applicable mass schedule.

Gross combination mass (GCM) must not exceed the lesser of the vehicle's rated GCM and the applicable legal combination limit.

Load restraint: the load must be restrained so it will not shift under braking, acceleration, cornering or vibration; the restraint system must be rated for the load's mass.

Tie-down capacity rule: the aggregate lashing capacity must be at least the load mass for forward restraint, with additional capacity for lateral and rearward restraint depending on the standard applied.

Height, width and length limits vary by jurisdiction; overlength or overwidth combinations require permits and may require pilot or escort vehicles.

Axle group load sharing: poorly distributed loads can overload one axle while the total mass is legal; weighbridge checks measure per-axle and per-group loads, not just total.

Load restraint records and mass declarations must be accurate; a consignor who provides a false mass declaration can be liable under COR.

Fatigue-regulated heavy vehicle drivers must comply with work and rest hour limits set by the applicable national or state fatigue rules; the stricter of the applicable rules governs.

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

A common minimum rest break rule: after a set period of work (for example 5 to 5.5 hours), a minimum continuous rest break (for example 30 minutes) is required.

Solo drivers typically have a maximum continuous work period and a maximum daily work limit; these differ for solo, solo-with-passenger, and two-up operations.

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

Fatigue is a hazard even within legal hours: signs include micro-sleeps, lane drift, yawning, and difficulty focusing; the driver must stop and rest rather than push on.

Night driving between roughly midnight and 6 am carries higher fatigue risk and may attract additional rest requirements under some fatigue schemes.

The operator must schedule runs so that legal work and rest limits can be met; scheduling that makes compliance impossible is a COR breach.

Air-brake system components: compressor, governor, reservoirs, foot valve, relay valves, slack adjusters, brake chambers and spring (parking) brakes.

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

Governor cut-out is typically around 100-120 psi; cut-in is typically around 85 psi; pressure below the warning threshold (often around 60-65 psi) triggers a low-pressure warning.

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.

Air dryer and moisture: water in the air system can freeze in cold weather and cause brake failure; daily draining of reservoirs and functioning air dryers are required.

Trailer brake coupling: the trailer's emergency (supply) line must be connected and charged before the trailer brakes will release; a broken supply line applies the trailer spring brakes.

Anti-lock braking systems (ABS) prevent wheel lock-up but do not shorten stopping distance on all surfaces; the driver must still brake firmly and steer.

Brake test before a descent: check that the system holds pressure, that the low-pressure warning works, and that the parking brake holds the loaded vehicle on a grade.

Centre of gravity (CoG) height: raising the CoG by loading high increases rollover risk; the rollover threshold is roughly the track width divided by twice the CoG height.

Load transfer in a turn is proportional to CoG height and lateral acceleration; a heavy vehicle can roll over before the tyres lose grip.

Rearward load bias reduces steer-axle load and can cause understeer or loss of steering grip; forward bias can overload the steer axle and reduce traction on the drive axles.

Articulated combinations: a lightly loaded trailer or a poorly coupled trailer can cause jack-knifing under heavy braking, 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 and the wider the turn needed.

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

Crosswinds and passing high-sided vehicles create lateral forces on tall loads; reduce speed and increase lane clearance in strong wind.

Downhill speed control: select a gear that holds a safe speed without continuous service braking, and use engine or retarder braking to avoid fade.

Scan pattern: look well ahead (roughly 12-15 seconds of travel), check mirrors every few seconds, and monitor the blind spots on both sides of the vehicle.

Following distance rule: at least 4 seconds behind the vehicle ahead at highway speed, doubled in rain or low visibility; heavy vehicles need more distance than cars.

Blind spots: a heavy vehicle has large blind areas directly in front, behind and alongside; a passing vehicle may be invisible even when the driver checks mirrors.

Intersection hazard: heavy vehicles need more time and distance to stop, so approach intersections at a speed that allows a stop within the visible clear distance.

Pedestrians and cyclists near the left or right front corner are a high-risk hazard; check mirrors and use turn signals early before turning.

Speed choice: drive to the conditions (visibility, road surface, load, traffic) rather than the posted limit; the posted limit is a maximum, not a target.

Distraction: mobile phone use, navigation adjustments and eating while driving are prohibited or restricted; plan stops for these tasks.

Hazard perception is predictive: identify the developing hazard (a vehicle slowing, a pedestrian approaching a crossing) and adjust speed before the hazard becomes urgent.

After a crash: stop, secure the scene, check for injuries, call emergency services, and exchange details; do not leave the scene unless legally permitted.

Fire: switch off the engine, isolate the battery if safe, evacuate upwind, and do not open a hot engine cover fully; heavy-vehicle fires can involve fuel and load hazards.

Runaway vehicle: use engine braking, a lower gear, and if necessary the emergency escape ramp or a safe runoff area; do not ride the service brakes continuously.

Spill or load loss: secure the area, warn other traffic, notify the operator and emergency services, and do not attempt to move hazardous loads without trained personnel.

Incident reporting: record time, location, vehicles involved, injuries, damage and any defect or fatigue factor; the operator must report notifiable incidents to the regulator.

Chain of responsibility after an incident: the regulator may investigate the consignor, packer, loader, driver and operator; each party must show it took reasonable steps to prevent the breach.

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

Emergency equipment: heavy vehicles should carry a fire extinguisher, warning triangles or reflectors, and a first-aid kit as required by the jurisdiction.