NJ CDL General Knowledge key terms

A required walk-around check of lights, tires, brakes, fluids, coupling devices, and cargo before driving, intended to catch defects that could cause a breakdown or crash while the vehicle is still parked.

A sequence of checks performed before driving that confirms the air compressor builds pressure, leaks stay within limits, and the warning buzzer and spring brakes engage at the correct low-pressure points.

The speed at which the compressor raises tank pressure at governed engine speed, typically required to reach a specified gain within a set time; slow build-up signals a compressor or leak problem.

Parking and emergency brakes held applied by heavy mechanical springs and released by air pressure, so they set automatically when air pressure drops too low or lines fail.

The lever arm between the brake chamber pushrod and the brake shoe that multiplies force; excessive pushrod travel or a loose adjuster means weak or uneven braking and must be corrected before driving.

How far the brake chamber rod extends when the brakes are applied; too much travel wastes air and reduces stopping force, so it is measured during inspection against the manufacturer's limit.

The air cylinder that converts air pressure into mechanical force on the brake linkage; a cracked housing, bad clamp band, or leaking diaphragm makes the brake unsafe.

A technique for vehicles without antilock brakes in which the driver applies the brake firmly and fully, releases when wheels lock, and reapplies, avoiding a long light drag that overheats brakes.

Loss of stopping power when brakes overheat from repeated or prolonged use, common on long downgrades; the cure is engine braking and a low gear, not harder pedal pressure.

A device such as a Jake brake or exhaust brake that uses engine compression to slow the vehicle on grades, saving service brakes from heat; it may be restricted near residences.

Choosing a low gear before starting a long descent and staying in it, so engine braking holds speed and service brakes are used only briefly; shifting mid-grade risks runaway speed.

An electronic system that senses wheel lockup and rapidly modulates brake pressure to keep wheels rolling, preserving steering control during hard stops on slippery surfaces.

Loss of tire grip in which the wheels slide rather than roll, caused by braking too hard, accelerating too fast, or turning too sharply for the road surface.

A combination-vehicle skid in which the tractor and trailer fold toward each other, usually after the drive or trailer wheels lock; recovery requires releasing the brakes and steering to straighten.

Side-to-side fishtailing of a trailer, often from too little weight on the tow vehicle's rear axle, crosswinds, or speed; easing off the accelerator and steering straight helps regain control.

Applying brake pressure up to just short of wheel lockup and holding it there, which produces maximum stopping force while keeping some steering ability.

The gap kept behind the vehicle ahead, measured in seconds by counting after it passes a fixed object; large trucks need at least one second per ten feet of length plus extra margin.

The margin of clear space kept around the vehicle on all sides so there is room to stop or swerve when traffic, road, or visibility changes suddenly.

Total distance needed to halt, made up of perception distance, reaction distance, and braking distance; it grows with speed, weight, and slippery pavement.

Matching travel speed to road, weather, visibility, and load, and choosing a gear that keeps the engine in its power band so the vehicle can accelerate or hold a grade safely.

Scanning far down the road and to the sides, not just at the vehicle ahead, to spot hazards, signals, and lane changes early enough to respond smoothly.

Regular glances at both flat and convex mirrors to track traffic beside and behind the vehicle, especially before changing lanes, turning, or backing.

The area beside and behind the vehicle that mirrors do not show; a driver must know its size and check it by turning the head or using a spotter before moving over.

A person outside the vehicle who guides a driver during backing or tight maneuvers using agreed hand signals, stopping the vehicle if the driver loses sight of them.

Driving in reverse, the highest-risk maneuver for large vehicles; it should be avoided when possible, done slowly, and always with a look to the rear or a spotter.

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

The outward sweep of a long vehicle's rear end during a turn, which can strike nearby objects or vehicles; it is controlled by starting the turn wide and moving slowly.

Approaching a right turn by moving into the proper lane, checking mirrors and blind spots, and turning wide enough that the rear wheels clear the curb without crowding other traffic.

Shifting a non-synchronized manual transmission by pressing the clutch, shifting to neutral, releasing, matching engine speed, then pressing the clutch again to engage the next gear.

Shifting a manual transmission without using the clutch by matching engine and road speed precisely; it demands skill and is not recommended for inexperienced drivers.

Adjusting engine speed to the gear being selected so the transmission engages smoothly without clashing or jerking, protecting gears and keeping the vehicle stable.

The horseshoe-shaped coupling plate on a tractor that locks onto the trailer kingpin; it must be inspected for proper engagement, grease, and a closed locking jaw.

The vertical pin under a trailer's front that locks into the tractor's fifth wheel; a worn or improperly seated kingpin can let the trailer separate from the tractor.

The retractable legs supporting a detached trailer; they must be fully raised and secured before moving, and crank handles stowed so they do not strike anything.

The system of tiedowns, straps, chains, and blocking that keeps cargo from shifting, falling, or spilling; it must match the load's weight and be checked during the trip.

A strap, chain, or rope used to anchor cargo to the vehicle; the required number and strength depend on the load's weight and length and on the type of article.

The maximum load a tiedown or securement device is rated to hold in service; aggregate tiedown capacity must at least equal half the cargo weight under the general rule.

Placing cargo so weight is balanced across axles and stays within axle and gross limits, keeping enough weight on steering and drive axles for control and traction.

The maximum total weight a vehicle or combination is designed to carry, including chassis, body, fuel, driver, and cargo; exceeding it is both unsafe and illegal.

The maximum load allowed on a single axle or axle group, set by the manufacturer and by law; overloading an axle reduces braking and steering control.

Federal rules limiting driving and on-duty time and requiring rest periods, tracked in a log or electronic record, to prevent fatigue-related crashes.

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

The employer-kept record proving a driver is eligible, including application, motor vehicle record, medical certificate, road test or equivalent, and annual review documents.

A document from a qualified examiner stating the driver meets physical qualification standards; without a valid certificate the driver may not operate a commercial vehicle.

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

The legal principle that holding a commercial license means agreeing to submit to alcohol or drug testing when lawfully requested; refusal carries license penalties.

A directive barring a driver or vehicle from operating until a violation is corrected, such as an hours violation, serious defect, or impairment finding.

The eyes' reduced ability to see detail and color in dim light; glare recovery slows with age, so drivers should reduce speed and increase following distance after dark.

The time the eyes need to readjust after oncoming headlights or bright light; looking toward the right edge of the lane shortens the effect and keeps the vehicle tracking straight.

Running low beams in darkness, rain, fog, or snow and dimming for oncoming traffic; high beams are for open dark roads but worsen visibility in fog.

Riding on a film of water so tires lose contact with the pavement, causing loss of steering and braking; easing off the accelerator and avoiding hard braking restores grip.

The skill of scanning for developing risks such as merging traffic, stopped vehicles, or pedestrians and deciding early whether to slow, change lanes, or sound a warning.

A gravel or sand ramp beside a steep downgrade for vehicles that lose braking; steering into it and staying straight lets the surface slow the vehicle safely.