Alberta Class 4 key terms

A qualification added to a Class 4 licence that permits driving vehicles equipped with air brakes, requiring a knowledge test and a practical air brake adjustment check.

The correct setting of slack adjusters so pushrod travel stays within the manufacturer's limit; excessive travel reduces braking force and is a common defect found in inspections.

The distance an air brake chamber pushrod extends when the brake is applied. Measuring it with a rule shows whether the slack adjuster needs adjustment or the brake is out of service.

A systematic walk-around and in-cab check of lights, tires, brakes, fluids, couplings and load before driving, intended to catch defects while the vehicle is still stationary and safe.

A check completed at the end of a trip, or at the end of each day, recording defects so they can be reported and repaired before the vehicle is used again.

A written record of a mechanical problem found during inspection, signed and given to the carrier so repairs can be scheduled and the vehicle kept out of service until fixed.

A defect serious enough that the vehicle must not be driven until repaired, such as a broken spring, a leaking air line, or a brake that will not hold.

The measured thickness of remaining tread rubber; worn tread reduces traction and increases hydroplaning risk, and legal minimums apply to steering and drive tires.

The use of straps, chains, binders and anchor points to hold cargo so it cannot shift, fall or spill, keeping the vehicle stable and protecting other road users.

An individual strap, chain or webbing assembly that fastens cargo to the vehicle; the required number depends on the length and weight of the load.

The maximum load a tiedown or fitting is rated to carry continuously, marked by the manufacturer; the total capacity of all tiedowns must exceed the cargo weight.

The sum of the working load limits of all tiedowns used on a load; regulations require this total to be at least half the weight of the cargo secured.

Movement of cargo while driving, which can change weight distribution, affect steering and braking, and cause a rollover; prevented by proper securement and blocking.

The point where a vehicle's weight is balanced; a high or off-centre point of gravity, common with tall or poorly loaded cargo, makes rollover more likely in turns.

A crash in which the vehicle tips onto its side or roof, often caused by taking a curve too fast, sudden steering, or a high centre of gravity.

Choosing a speed low enough that the vehicle can stay in its lane through a bend; posted curve warnings often show a safe speed for cars, so heavier vehicles should go slower.

The gap kept behind the vehicle ahead, measured in seconds; large or heavy vehicles need a longer gap because stopping distance grows with weight and load.

The total distance travelled from seeing a hazard to coming to a full stop, made up of perception, reaction and braking distance, all increased by speed and weight.

Loss of braking power when brakes overheat, common on long downgrades; controlled by gearing down and using engine braking rather than riding the service brakes.

Using a lower gear so the engine's compression slows the vehicle, reducing reliance on the service brakes and helping prevent overheating on long or steep descents.

A gravel escape ramp built beside a steep downgrade for drivers who lose braking control, allowing the vehicle to be stopped safely by rolling resistance.

The clear area kept around the vehicle on all sides so there is room to react, change lanes or stop if another road user makes a sudden move.

An area around the vehicle that cannot be seen in the mirrors; large vehicles have wide blind spots, so drivers must check carefully and shoulder-check before turning or changing lanes.

A hazard where a large vehicle swings left before turning right, and a cyclist or pedestrian moves into the open gap on the right side and is struck.

The tendency of the rear wheels of a long vehicle to follow a tighter path than the front wheels, so the rear can clip curbs, poles or adjacent lanes in a turn.

The outward movement of the rear of a long vehicle during a turn; drivers must allow extra room so the back end does not strike people or objects at the corner.

Rules limiting how long a commercial driver may drive and work without rest, designed to reduce fatigue-related crashes and recorded in a daily log.

A record of a driver's on-duty, driving, off-duty and sleeper hours for each day, kept current and available for inspection by enforcement officers.

The maximum on-duty time a driver may accumulate over a set number of consecutive days before taking required reset time off.

A driver's physical and mental readiness to operate a vehicle, covering fatigue, illness, medication, alcohol and stress, all of which impair judgement and reaction time.

A state of reduced alertness from lack of sleep or long hours, causing slower reactions and poor decisions; managed with rest breaks, limits on driving time and recognizing warning signs.

A vehicle such as an ambulance, fire truck or police car using lights or siren; drivers must yield, pull to the right and stop when it approaches.

The flashing red signal extended by a school bus picking up or dropping off children; traffic in both directions must stop until the arm is withdrawn, unless divided by a median.

A place where the road meets train tracks; drivers must slow, look and listen, never stop on the tracks, and obey lights, gates and crossbucks.

The maximum weight a vehicle, axle or tire is designed to carry safely, set by the manufacturer; exceeding it affects handling, braking and legal compliance.

The share of a vehicle's total weight carried by one axle; overloading an axle or exceeding tire ratings is unsafe and can result in fines or being ordered off the road.

A periodic safety inspection of a commercial vehicle by a certified inspector, confirming brakes, lights, steering, tires and structure meet required standards.