Montana CDL General Knowledge key terms

A systematic check of a commercial vehicle's critical parts and systems before driving, covering lights, tires, brakes, coupling devices, fluids, and emergency equipment, performed to catch defects that could cause a breakdown or crash.

The maximum allowable pushrod travel for a given brake chamber size and type; exceeding it means the brake is out of adjustment and the vehicle must be placed out of service until corrected.

A static check with the system charged and the engine off, confirming that air pressure loss over one minute stays within the allowable limit with brakes released and again with the service brake applied.

An audible and visual alert that must activate before pressure drops below a set threshold, warning the driver that braking force is fading and a safe stop must be made immediately.

A parking and emergency brake held engaged by a powerful spring and released by air pressure; if air pressure is lost, the spring applies the brake automatically to stop the vehicle.

The lever linking the brake chamber pushrod to the brake shoe; its angle and pushrod travel indicate whether the foundation brake is properly adjusted and working.

The total distance traveled from the moment a hazard is recognized until the vehicle stops, combining perception, reaction, and braking distance and growing with speed and weight.

The gap maintained behind the vehicle ahead, measured in seconds by counting from when that vehicle passes a fixed object until your own vehicle reaches it.

The safety margin kept around the vehicle on all sides, including front, rear, and lateral gaps, so there is room to maneuver or stop when traffic, road, or visibility conditions change suddenly.

The distance covered while the driver notices and identifies a hazard before physically reacting; it grows with speed, fatigue, and distraction and is the first part of total stopping distance.

The distance traveled during the time between recognizing a hazard and applying the brake or steering input, typically about three-quarters of a second for an alert driver.

The placement of the vehicle within a lane, chosen to preserve clearance from parked cars, pedestrians, opposing traffic, and roadside hazards while keeping a stable path through curves and turns.

The tendency of a vehicle's rear wheels to follow a tighter path than the front wheels during a turn, requiring the driver to swing wide enough to keep the trailer off curbs and other objects.

The outward sweep of a vehicle's rear end or trailer during a turn, which can strike signs, poles, or adjacent vehicles if the turn is started too early or taken too sharply.

A shifting technique for non-synchronized manual transmissions in which the clutch is pressed once to leave a gear, released in neutral, then pressed again to engage the next gear at matched engine speed.

Shifting a non-synchronized transmission without using the clutch by matching engine and road speed; it requires skill and is not recommended for inexperienced drivers or on unfamiliar equipment.

An economy technique of upshifting at lower engine rpm and downshifting at higher rpm as road speed rises, keeping the engine in its most efficient range and reducing fuel use and wear.

The engine speed limiter that cuts fuel or limits power at a set maximum; drivers must shift before reaching it and downshift before engine speed falls too low to pull the load.

Operating an engine at too low an rpm for the load, causing rough running, poor power, and potential damage; the driver should downshift to restore pulling power and protect the drivetrain.

Backing from a street into a narrow dock area between buildings; it is done slowly with a spotter or by stopping and rechecking, using mirrors and reference points to avoid hitting walls.

Get Out And Look: the practice of stopping, exiting the cab, and visually inspecting the path before continuing a backing maneuver when clearance or alignment is uncertain.

A person outside the vehicle who guides a backing or turning maneuver with agreed hand signals, staying visible in the mirrors and stopping the driver if the path is unsafe.

Loss of tire traction in which the vehicle slides instead of rolling; recovery requires releasing the brake or throttle, steering in the direction of the slide, and reestablishing control smoothly.

A dangerous condition in which the tractor and trailer fold against each other, often caused by locking the drive wheels or oversteering during a skid on slippery or loose surfaces.

The grip between tires and road surface; it is reduced by rain, ice, snow, gravel, and worn tread, so the driver must slow down and increase following distance when grip is poor.

A loss of contact between tires and pavement caused by water buildup under the tread; steering and braking become ineffective until speed drops and the tires regain contact.

A specially built uphill ramp with deep gravel or sand for drivers who lose braking on a downgrade, designed to stop a runaway vehicle safely without striking traffic or structures.

Loss of braking power caused by overheating from prolonged or repeated brake use, especially on downgrades; the cure is to slow down, use a lower gear, and let the brakes cool.

Using a lower gear so the engine's compression slows the vehicle on a downgrade, reducing reliance on the service brakes and helping prevent overheating and fade.

The system of tiedowns, straps, chains, and blocking used to keep cargo from shifting, sliding, or falling; it must meet working load limits and be checked during the trip.

The combined strength rating of all tiedowns securing a load; the total must be at least half the weight of the cargo, and each article must be secured against movement.

Movement of cargo during transit that can change axle weight distribution, destabilize the vehicle in turns, or cause the load to fall; prevented by proper blocking, bracing, and tiedowns.

The maximum total weight a vehicle or combination is designed to carry, including the vehicle, fuel, cargo, and passengers; exceeding it can overload tires, brakes, and axles.

A federal rule limiting the weight carried on any group of axles based on the number of axles and the distance between them, preventing concentrated loads from damaging bridges.

The maximum load allowed on a single axle or axle group, set by federal and state law and by tire and suspension ratings; exceeding it requires redistributing or removing cargo.

Federal rules limiting driving and on-duty time and requiring rest periods, tracked in a record of duty status, to prevent fatigue-related crashes among commercial drivers.

An onboard system that automatically records driving time and duty status, replacing paper logs for most carriers and helping enforce hours-of-service limits accurately.

Physical and mental tiredness that slows reaction time, impairs judgment, and increases crash risk; managed through adequate sleep, scheduled breaks, and recognizing warning signs like yawning and drifting.

The body's internal clock that creates natural drowsiness during nighttime hours, making late-night and early-morning driving especially risky for commercial drivers.

The measured amount of alcohol in the bloodstream; commercial drivers are held to a lower legal limit than other drivers, and any detectable level can trigger out-of-service action.

The legal principle that by driving on public roads a driver agrees to submit to alcohol and drug testing when lawfully requested; refusal carries license penalties.

Alcohol or drug testing required when a trained supervisor observes specific, articulable signs of impairment, such as slurred speech, odor, or erratic driving, in a safety-sensitive employee.

An intersection of road and rail tracks where drivers must slow, look, and listen, never stop on the tracks, and ensure there is room to clear the crossing completely before proceeding.

A railroad crossing device that signals an approaching train, such as flashing lights, bells, or gates; drivers must stop when activated and never drive around lowered gates.

A railroad crossing sign or marking that does not change with train traffic, such as the round yellow advance warning sign, crossbuck, or pavement markings indicating track location.

The area around a stopped school bus with flashing red lights and an extended stop arm, where drivers in both directions must stop unless separated by a physical median or barrier.

The swing-out sign on a school bus that extends with flashing red lights to signal traffic to stop while children board or exit; passing it unlawfully carries heavy penalties.

Amber lights warning that a school bus is preparing to stop, followed by red lights requiring traffic to stop; drivers must anticipate children and never pass a bus displaying red lights.