Missouri CDL General Knowledge key terms

A systematic check of critical vehicle parts, including brakes, tires, lights, and coupling devices, performed before driving to confirm the vehicle is safe and defects are corrected.

A written report the driver prepares after each pre-trip or post-trip inspection listing any defects found that could affect safety or lead to a breakdown.

A safety defect serious enough that federal or state rules prohibit operating the vehicle until it is repaired, such as a brake pushed beyond its adjustment limit.

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

The lever that connects the brake chamber pushrod to the brake shoe; its angle and pushrod travel show whether the brake is properly adjusted.

A braking system that uses compressed air to apply the brakes, requiring the driver to build pressure, check for leaks, and understand warning signals before driving.

A buzzer and light that must activate before air pressure drops below a set level, warning the driver that braking power is being lost.

Brakes held applied by powerful springs and released by air pressure; they apply automatically when pressure falls too low or the parking brake is set.

The total distance a vehicle travels from the moment a hazard is seen until it stops, including perception, reaction, and braking distance.

The distance a vehicle travels while the driver recognizes a hazard and decides to act, before the foot reaches the brake.

The gap between your vehicle and the one ahead, measured in seconds by counting from when the rear of the leading vehicle passes a fixed point.

The safety margin kept around the vehicle on all sides so there is room to stop or maneuver if traffic, road, or load conditions change suddenly.

The placement of the vehicle within a lane, chosen to keep clearance from other traffic, parked cars, and roadside obstacles while maintaining a safe path.

The tendency of the rear wheels of a long vehicle to follow a tighter path than the front wheels, requiring wider turns to avoid hitting curbs or objects.

The outward sweep of the rear of a long vehicle during a turn, which can strike signs, poles, or vehicles on the outside of the curve.

The maneuver of swinging left before a right turn so the rear wheels clear the curb, while checking mirrors and signaling to protect other traffic.

A shifting method for non-synchronized transmissions in which the clutch is pressed twice, once to leave a gear and once to engage the next, matching engine speed.

Shifting without using the clutch by matching engine and transmission speed, a technique some experienced drivers use but that risks gear damage if speeds are mismatched.

A fuel-saving method of upshifting at lower engine rpm, used only on engines and transmissions designed for it, to reach cruising gear sooner.

Loss of traction in which tires slide instead of roll, often caused by braking too hard, accelerating too fast, or turning too sharply on a slippery surface.

Turning the steering wheel in the direction the rear of the vehicle is sliding to regain control during a skid, then straightening as traction returns.

The grip between tires and the road surface; it is reduced by rain, ice, snow, gravel, and worn tires, increasing stopping distance and skid risk.

A condition in which tires ride on a layer of water and lose contact with the road, causing loss of steering and braking control.

A specially built ramp with a gravel or sand bed that lets a driver with failing brakes stop safely, typically found on long downgrades.

Loss of braking power caused by overheating, often from riding the brakes on a long downgrade, which requires slowing down and using a lower gear.

Using a lower gear to let engine compression slow the vehicle, reducing reliance on wheel brakes and helping prevent brake fade on downgrades.

A place where a road crosses train tracks; drivers must slow down, look and listen, and never stop on the tracks.

A crossing signal that warns of an approaching train, such as flashing lights, bells, or gates, which must be obeyed even if no train is visible.

A fixed sign or marking at a crossing, such as a crossbuck or pavement markings, that identifies the crossing but does not change with train traffic.

The system of tiedowns, straps, chains, and blocking used to keep cargo from shifting, falling, or spilling during normal driving and emergencies.

The combined strength rating of all tiedowns used on a load, which must meet minimum rules based on the weight and type of cargo.

A strap, chain, rope, or other device used to anchor cargo to the vehicle; each has a working load limit that must not be exceeded.

Federal and state limits on driving and on-duty time, including daily driving limits and required rest periods, designed to reduce driver fatigue.

An automatic onboard recorder that tracks driving time and duty status, replacing paper logs for most commercial drivers.

Physical or mental exhaustion that slows reaction time and judgment; drivers must rest rather than rely on caffeine or open windows to stay alert.

The body's natural sleep-wake cycle, which causes predictable low-alertness periods, especially at night and in early afternoon, raising drowsy-driving risk.

The percentage of alcohol in the blood, used as the legal measure of impairment; commercial drivers are held to a stricter limit than other drivers.

The rule that a licensed driver agrees in advance to submit to alcohol or drug testing when lawfully requested, with penalties for refusal.

Alcohol or drug testing required when an employer has specific, observable evidence that a driver may be impaired or has violated drug and alcohol rules.