Ontario Class A Commercial key terms

A systematic walk-around and in-cab check of a commercial vehicle completed before driving, confirming brakes, lights, tires, coupling, load securement and fluids are safe and compliant. Defects found must be corrected or reported before the vehicle is operated.

A stationary check with the system charged and engine off, observing gauge drop over a set period with brakes released and then applied. Excessive pressure loss indicates a leak that must be repaired before the trip begins.

An audible and visual alert that activates when reservoir pressure falls below the manufacturer's threshold, warning the driver that braking performance is degrading. The vehicle must not be driven until pressure builds to normal operating range.

A fail-safe parking and emergency brake held applied by a heavy spring and released by air pressure. Loss of air pressure causes it to apply automatically, so a vehicle with a serious leak cannot be driven safely.

The linkage between the brake chamber pushrod and the brake shoe that transfers force. Excessive pushrod travel means the brakes are out of adjustment and stopping distance increases, so it is checked during inspection.

Loss of braking power caused by heat buildup in drums or discs during prolonged or repeated application, common on long downgrades. It is prevented by gearing down and using intermittent braking rather than riding the brakes.

The regulated limits on driving and on-duty time within a day and a cycle, designed to prevent fatigue. Drivers must track driving, on-duty, off-duty and sleeper time and stop driving when a limit is reached.

A record of a driver's duty status through the day, showing driving, on-duty not driving, off-duty and sleeper berth periods, plus vehicle, distance and carrier information. Entries must be current, accurate and retained for the required period.

The required off-duty period that clears accumulated on-duty time so a driver can begin a fresh cycle. It must meet the minimum consecutive hours set by the jurisdiction before the new cycle starts.

A device that automatically records driving time by syncing with the engine, replacing paper logs for most carriers. Drivers must still review, certify and annotate records, and carry required backup documentation.

The system of straps, chains, binders, tarps and blocking used to hold a load so it cannot shift, fall or leak in transit. It must meet working load limits and be checked during the trip, not just at loading.

The maximum load a single tie-down, strap, chain or fitting is rated to carry, marked by the manufacturer. It is not the breaking strength; securement calculations use this rated value.

The total of the working load limits of all tie-downs used on a load. Regulations require the aggregate to equal at least half the weight of the cargo, and more tie-downs are needed as load weight rises.

The minimum number of separate securement devices required for a load, set by cargo weight and length. Each tie-down must be attached to the vehicle and the cargo and be independently tensioned.

A strong barrier at the front of a flatbed or trailer that stops cargo from sliding forward against the cab during braking. It supplements, but does not replace, proper tie-downs.

Movement of cargo during transit caused by inadequate securement, poor weight distribution or sudden manoeuvres. It can change axle weights, destabilize handling and cause loss of control or spillage.

The maximum total weight a vehicle or combination is designed to carry, including chassis, body, fuel, occupants and cargo, set by the manufacturer. Exceeding it is unsafe and may be charged as an overweight offence.

The portion of total vehicle weight carried by a single axle or axle group. Each axle has a rated limit, and overloading one axle can damage pavement, reduce steering or traction and trigger penalties.

Placing cargo so that weight is balanced across axles and kept low and centred. Poor distribution overloads axles, lightens the steering axle and makes the combination prone to sway or jackknife.

An authorization allowing a vehicle to exceed normal weight or dimension limits for a specific trip, route and time. The permit states conditions such as escorts, travel hours and approved roads that must be followed exactly.

A load whose width, height or length exceeds legal limits and therefore needs a permit, markings and often escorts. Height must be checked against clearances and width against lane and bridge restrictions.

An escort vehicle travelling ahead of or behind an over-dimensional load to warn traffic and assist with manoeuvres. Requirements for number, position, signage and lighting depend on the load's dimensions and route.

The horseshoe-shaped coupling plate on a tractor that locks onto the trailer kingpin. It must be greased, properly latched and visually checked with a tug test before the combination is driven.

The vertical pin under a trailer that locks into the tractor's fifth wheel. The locking jaws must close fully around it, confirmed by a pull test and a visual check of the release handle.

A check after coupling where the driver applies low power against the trailer with the trailer brakes set, confirming the fifth wheel is locked and will not release. Any movement means the coupling is unsafe.

The retractable legs supporting a parked trailer. They must be fully raised before driving and fully lowered and pinned before uncoupling, or the trailer can drop and the tractor can be damaged.

The coupling of the tractor's service and supply gladhands to the trailer, usually colour-coded for correct pairing. Crossed lines cause brake failure or trailer brake lock-up, so lines are checked after coupling.

The tendency of a trailer's rear wheels to cut inside the path of the tractor during a turn. Drivers must swing wide and watch mirrors to avoid striking curbs, poles or vehicles beside them.

Steering a combination vehicle outward before and through a turn so the trailer clears curbs, signs and adjacent traffic. The manoeuvre must be balanced against the risk of crossing into oncoming lanes.

An area around a heavy vehicle that the driver cannot see in mirrors, especially alongside and directly behind the trailer. Other drivers should be assumed present there, and lane changes require deliberate mirror checks.

The gap kept behind the vehicle ahead, measured in seconds and increased with speed, load and poor conditions. Large vehicles need far more space than cars to stop, so a longer gap is the primary defence.

The total distance travelled from perceiving a hazard to coming to rest, combining reaction distance and braking distance. It rises sharply with speed, weight and wet or icy surfaces.

The buffer of clear space kept around a heavy vehicle on all sides so there is room to react or escape. It is maintained by adjusting speed, lane position and following distance continuously.

An escape ramp of gravel or rising grade beside a steep downgrade that stops a vehicle whose brakes have failed. Drivers should use it early rather than risk a high-speed crash further down.

A controlled, firm application of the brakes, often with the trailer brake hand valve, to stop quickly without locking wheels. Steering must be maintained while braking to keep the vehicle in its lane.

A defect listed in the provincial inspection standard that makes a vehicle unsafe to operate until repaired. Drivers must identify these during inspection and remove the vehicle from service if one is found.

A formal periodic or roadside examination of a commercial vehicle against safety standards, covering brakes, steering, lights, tires, frame and securement. It can result in defects being ordered repaired before further operation.