Delaware CDL General Knowledge key terms

The maximum safe loaded weight of a single vehicle, including its own weight plus fuel, cargo, and passengers, as set by the manufacturer. It determines whether a vehicle requires a CDL.

The maximum safe loaded weight of a towing vehicle plus its towed trailer or trailers combined, as specified by the manufacturer. It is used with the trailer rating to classify combination vehicles.

A CDL classification covering combination vehicles with a GCWR of 26,001 pounds or more, provided the towed unit exceeds 10,000 pounds. It permits operation of Class B and Class C vehicles with proper endorsements.

A CDL classification for a single vehicle with a GVWR of 26,001 pounds or more, or any such vehicle towing a unit not exceeding 10,000 pounds. It also covers Class C vehicles with endorsements.

A CDL classification for vehicles not meeting Class A or B definitions that are designed to carry 16 or more passengers including the driver, or that carry hazardous materials requiring placards.

An additional authorization added to a CDL that allows the driver to operate specific vehicle types or carry specific cargo, such as passengers, tankers, doubles, or hazardous materials.

An endorsement required to drive a vehicle carrying placarded quantities of hazardous materials. It requires a background check and a passing score on the hazardous materials knowledge test.

An endorsement required to drive a commercial vehicle designed to carry 16 or more people, including the driver. It requires a knowledge test and a skills test in the appropriate vehicle.

An endorsement required to drive a commercial tank vehicle, which is a vehicle designed to carry liquid or gaseous materials in a permanently mounted tank. It requires a separate knowledge test.

A restriction placed on a CDL when the driver tests in a vehicle without air brakes, preventing operation of vehicles equipped with air brakes until the driver passes the air brake knowledge and skills tests.

A braking system that uses compressed air to apply the brakes. It includes a compressor, reservoirs, foot valve, and slack adjusters, and requires an air pressure build-up and leakage check.

A systematic check of a commercial vehicle's critical parts and systems performed before driving, covering brakes, lights, tires, coupling devices, and emergency equipment. Passing this inspection is part of the CDL skills test.

The portion of the pre-trip inspection in which the driver physically circles the vehicle, checking tires, lights, fluid leaks, cargo securement, and coupling devices from the ground.

The total distance a vehicle travels from the moment a hazard is perceived until it comes to a complete stop. It combines perception distance, reaction distance, and braking distance.

The distance a vehicle travels while the driver recognizes that a hazard exists and decides what to do. It grows with speed and with driver fatigue or distraction.

The distance a vehicle travels between the moment the driver decides to brake and the moment the brake pedal is actually pressed. It increases with speed and driver reaction time.

The distance a vehicle travels from the moment the brakes are applied until it stops. It increases with speed and weight and is affected by road surface and brake condition.

The gap a driver keeps behind the vehicle ahead. For heavy commercial vehicles at highway speed, one common rule is at least one second for each 10 feet of vehicle length, plus one second.

The safety margin of clear space kept around a commercial vehicle so the driver has room to stop or maneuver if traffic ahead slows suddenly or a hazard appears.

The blind spots around a large commercial vehicle where the driver cannot see other vehicles. They exist on both sides, directly behind, and in front of the cab.

The proper setting of a commercial vehicle's mirrors so the driver can see the sides and rear of the vehicle and adjacent traffic lanes. Mirrors should be checked before each trip.

The forward or backward movement of liquid cargo inside a partly filled tank, which shifts the vehicle's center of gravity and can make it unstable or hard to stop.

The empty space left above a liquid in a tank. Too much outage allows liquid to surge and destabilize the vehicle, so tank loads are often kept nearly full.

A partition inside a tank that slows the movement of liquid cargo. Baffles reduce surge but do not eliminate it, so the driver must still brake and turn smoothly.

The horseshoe-shaped coupling plate mounted on a tractor that locks onto the trailer's kingpin. It must be checked for secure locking before the vehicle is moved.

The vertical pin mounted under a trailer that locks into the tractor's fifth wheel. A properly seated kingpin is essential to keep the trailer attached.

The process of connecting a tractor to a trailer, including aligning the fifth wheel, backing under the trailer, locking the kingpin, and testing the connection with a tug test.

A check performed after coupling in which the driver pulls gently forward with the trailer brakes set to confirm the kingpin is locked and the trailer will not separate.

The component that connects the brake chamber push rod to the brake shoe, transferring air pressure into braking force. Its travel must be within the manufacturer's limit for the brakes to work properly.

A warning signal, such as a buzzer or light, that activates when air pressure in the brake system falls below a safe level. The driver must stop and find the leak before continuing.

The loss of braking power that occurs when brakes overheat, often from repeated or prolonged use on long downgrades. Drivers should use engine braking and lower gears to avoid it.

A device that uses the engine's compression to slow the vehicle, reducing reliance on the service brakes. It is especially useful on long downgrades to prevent brake fade.

Shifting a vehicle into a lower gear to increase engine braking and control speed, especially on downgrades. The shift should be made before the vehicle gains too much speed.

The methods used to tie down and contain cargo so it cannot shift, fall, or spill during transit. Federal rules specify the number of tiedowns and the working load limit of the securement system.

The maximum load a tiedown or securement component is designed to hold safely. The combined working load limit of the tiedowns must be at least half the weight of the cargo.

The movement of cargo during transit, which can change the vehicle's balance and make it harder to steer or stop. Cargo must be secured to prevent shifting.

A diamond-shaped sign placed on a vehicle to warn others that it carries hazardous materials. Placards identify the hazard class and are required above certain quantities.

The documentation that accompanies a hazardous materials shipment, describing the material, its hazard class, and emergency response information. It must be kept within reach of the driver.

A place where a road crosses railroad tracks at the same level. Commercial drivers must slow down, look and listen, and never stop on the tracks.

A loss of tire traction in which the wheels slide instead of rolling. It can be caused by braking too hard, accelerating too fast, or turning too sharply on a slippery surface.