California CDL General Knowledge Test key terms

The maximum total weight a single vehicle can safely carry, including the vehicle itself, fuel, passengers, and cargo, as set by the manufacturer.

The maximum combined weight of a towing vehicle plus its trailer or trailers, including all cargo, fuel, and passengers, as set by the manufacturer.

The amount of weight carried by a single axle or a group of axles; it must stay within the axle rating and legal bridge-formula limits.

The methods and equipment, such as tiedowns, straps, chains, and blocking, used to keep cargo from shifting, sliding, or falling off the vehicle.

Placing cargo so its weight is balanced and within axle and gross weight limits; poor distribution can hurt steering, braking, and stability.

The point at which the weight of the vehicle and its load balances; a higher center of gravity increases the risk of rollover, especially in turns.

A diamond-shaped warning sign that must be displayed on a vehicle carrying certain hazardous materials in quantities that require placarding under federal rules.

A check of the vehicle's systems and parts before driving, including engine, brakes, lights, tires, coupling, and cargo, to find defects that could cause a breakdown or crash.

A visual check made by walking around the vehicle, looking at lights, tires, leaks, securement, and coupling before or during a trip.

An inspection at the end of the duty day; any defects must be recorded on a report and the vehicle repaired or taken out of service if unsafe.

A braking system that uses compressed air to apply the brakes; it includes a compressor, storage tanks, valves, lines, and brake chambers, and must be drained of moisture daily.

A lever linking the brake chamber pushrod to the brake camshaft; it takes up slack as brake shoes wear and is checked by measuring pushrod travel.

The short delay between pressing the brake pedal and the brakes actually applying; in air brakes it is about 0.3 to 0.5 seconds and adds to stopping distance.

The total distance traveled from the moment a hazard is seen until the vehicle comes to a complete stop, including perception, reaction, and braking distance.

The gap between your vehicle and the one ahead; at minimum allow one second for each 10 feet of vehicle length, and add more for speed or bad conditions.

A safe margin of empty space around your vehicle on all sides, giving you time and room to react if traffic stops or a hazard appears.

An area around the vehicle that cannot be seen in the mirrors; large trucks have big blind spots, so drivers must check mirrors and signal before turning or changing lanes.

A device that uses engine compression to slow the vehicle without using the service brakes; it helps control speed downhill but may be restricted in some areas.

A shifting method for manual transmissions without synchronizers: press the clutch to neutral, release it, press it again, and shift into the next gear.

A place where a road crosses train tracks; drivers must slow down, look and listen both ways, and stop when required, such as when carrying passengers or hazardous materials.

Warning devices placed behind a stopped vehicle to alert approaching traffic; three are required, set at increasing distances to give drivers time to react.

Federal rules that limit driving and on-duty time to reduce fatigue; they set daily driving limits, required breaks, off-duty periods, and recordkeeping requirements.

A category recorded in a log or electronic device, such as driving, on-duty not driving, off-duty, or sleeper berth, that determines how the hours-of-service limits apply.

An electronic logging device that automatically records driving time and duty status; most interstate commercial drivers must use one instead of paper logs.

A berth in the truck used for rest; qualifying sleeper-berth time can count toward required rest and can be paired under split-sleeper rules.

A required break of at least 30 minutes after 8 cumulative hours of driving without a qualifying interruption; it may be off-duty, sleeper berth, or on-duty not driving.

The rule that a driver may drive no more than 11 hours after 10 consecutive hours off duty; driving beyond that is an hours-of-service violation.

The rule that a driver cannot drive beyond the 14th consecutive hour after coming on duty; off-duty breaks do not extend this window except under split-sleeper rules.

The maximum on-duty time allowed in 7 consecutive days (60 hours) or 8 consecutive days (70 hours); a 34-hour restart can reset the cycle.

Driving a commercial vehicle for personal use while off duty, such as commuting or moving to a restaurant; it must not advance the load and is subject to carrier rules.

A loss of traction in which the tires slide instead of rolling; the driver should steer in the direction of the skid and avoid hard braking.

A condition where tires ride on a film of water and lose contact with the road; it reduces steering and braking, so slow down in heavy rain.

A dangerous situation where the trailer swings out of line with the tractor, often during hard braking or a skid, and can block the road.

A sudden loss of tire air pressure; the driver should hold the steering wheel firmly, ease off the accelerator, and slow gradually without hard braking.

An emergency ramp, often gravel or sand, built to stop a vehicle that has lost its brakes on a downgrade; drivers should use it rather than risk a crash.

An official order that a vehicle or driver cannot operate because of serious safety violations; the driver must comply and correct the problem before moving.

Any activity that takes a driver's eyes, hands, or attention away from driving, such as texting, phone use, eating, or adjusting devices.

Extreme tiredness that slows reaction time and judgment; it is managed with adequate rest, hours-of-service limits, breaks, and good sleep habits.