New Mexico CDL General Knowledge key terms

The total distance a vehicle travels from the moment a hazard is seen until it comes to a complete stop. It equals perception distance plus reaction distance plus braking distance, and it grows quickly as speed increases.

The distance traveled while your eyes and brain recognize that a hazard exists. It depends on alertness and visibility, and it is the first part of total stopping distance.

The distance covered between recognizing a hazard and actually pressing the brake pedal. A tired, distracted, or impaired driver adds many feet here before any braking begins.

The distance needed to stop once the brakes are applied. It increases with speed and weight and is much longer on wet, icy, or gravel surfaces where tire traction is reduced.

The grip between tires and the road surface that allows steering, accelerating, and stopping. Rain, ice, snow, oil, and loose gravel all reduce traction and require slower speeds and gentler control inputs.

A condition where tires ride up on a layer of water and lose contact with the pavement, causing loss of steering and braking control. It is more likely at higher speeds, with worn tires, or in standing water.

The safety margin of empty space you keep around your vehicle so you have room to stop or maneuver if traffic changes suddenly. Following distance, lane position, and blind-spot awareness all build this cushion.

The gap between your vehicle and the one ahead. At highway speeds most large vehicles need at least one second per ten feet of vehicle length, plus extra time in bad weather or darkness.

An area around the vehicle that cannot be seen in the mirrors or through the windows. Large vehicles have large blind spots, so drivers must check mirrors and turn their heads before changing lanes.

The areas alongside, behind, and in front of a large vehicle where the driver cannot see other vehicles and where those vehicles cannot be seen. Staying out of these zones helps prevent sideswipes and rear-end crashes.

Operating a vehicle while attention is taken away by phones, food, navigation devices, or other tasks. Even a brief glance away at highway speed covers a long distance and sharply raises crash risk.

Physical or mental tiredness that slows reaction time, harms judgment, and can cause a driver to fall asleep at the wheel. Hours-of-service limits and rest breaks are designed to prevent it.

Loss of tire grip that makes the vehicle slide instead of tracking the driver's intended path. Recovery requires releasing the brake or accelerator and steering smoothly in the direction you want to go.

A skid in which the tractor and trailer fold toward each other at an angle, often after the drive wheels lock or the trailer pushes the tractor. It can make the combination uncontrollable and is common on slippery roads.

The system of tiedowns, straps, chains, and blocking used to keep cargo from shifting or falling off the vehicle. Federal rules set minimum working load limits and require the system to withstand forward, rearward, and sideways forces.

Any strap, chain, rope, or web assembly used to anchor cargo to the vehicle. Tiedowns must be in good condition, properly tensioned, and sufficient in number for the weight and length of the load.

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

Movement of cargo during transit caused by sudden stops, turns, or poor securement. It can change axle weights, damage the vehicle, and cause rollovers or loss of control.

The point where the weight of the vehicle and its load is balanced. A high or off-center center of gravity makes a vehicle more likely to roll over in turns or evasive maneuvers.

The amount of weight carried by a single axle or axle group. Overloading an axle is illegal and unsafe, so cargo must be placed and secured so no axle or tire rating is exceeded.

The maximum total weight a vehicle, including its load, is designed to carry safely, set by the manufacturer. Exceeding it stresses brakes, tires, and frame and violates weight laws.

A braking system that uses compressed air to apply the brakes. It includes a compressor, reservoirs, foot valve, brake chambers, and a parking brake that engages when air pressure drops too low.

The rate at which the compressor raises pressure in the reservoirs. A system in good condition should build from about 85 to 100 psi within 45 seconds at normal engine speed during the pre-trip check.

A check that the air brake system holds pressure when the engine is off and brakes are applied. With a full system, pressure loss should be no more than 3 psi in one minute for a single vehicle.

A buzzer and light that activate when reservoir pressure falls to about 60 psi or below. It warns the driver to stop safely before the spring brakes apply automatically from lost pressure.

A parking brake that uses a strong spring to apply the brakes when air pressure is released. Because the spring applies the brake, loss of air pressure causes the vehicle to brake automatically.

A test that the parking brake will hold the vehicle. With the vehicle on a grade and the brake set, the vehicle should not move when the engine is idled and the transmission is in a low gear.

A tractor pulling one or more trailers, joined by a fifth wheel and a coupling. It requires special handling because it is longer, heavier, and articulates at the connections.

The horseshoe-shaped plate on the tractor that the trailer kingpin locks into. It carries the trailer's weight and must be lubricated, properly positioned, and checked for a secure lock.

The pin on the trailer that locks into the tractor's fifth wheel. A proper coupling requires the kingpin to be fully seated with the locking jaws closed and the release handle in place.

The inspection after connecting a tractor and trailer to confirm the connection is secure. The driver checks the jaws, pulls the tractor gently against the trailer with the trailer brake set, and verifies air lines and landing gear.

The tendency of the rear wheels of a long vehicle to follow a path inside the front wheels when turning. It means the driver must swing wide and watch mirrors to keep trailers off curbs and other vehicles.

The way the last trailer in a multi-trailer combination swings farther sideways than the tractor during turns or lane changes. It makes doubles and triples harder to control and more prone to rollover.

A small axle assembly with a fifth wheel and a drawbar that connects a second or third trailer to the combination. It must be coupled and checked like any other trailer connection.

Combinations that pull two or three trailers. They need more stopping distance, are more affected by wind, and require careful brake and lane control because each trailer moves independently.

A vehicle with a permanently mounted tank or a portable tank of 119 gallons or more, used to carry liquids or gases. The moving liquid shifts weight and raises rollover risk.

The forward and backward movement of liquid in a partly filled tank when the vehicle speeds up, stops, or turns. It can push the vehicle and make braking and steering unpredictable.

An internal wall inside a tank that divides the liquid and limits how far it can surge. Baffles reduce the shifting weight effect but do not eliminate it, so smooth driving is still required.

Cargo that poses a risk to health, safety, or property, such as flammables, corrosives, oxidizers, or poisons. Transporting it requires proper placards, shipping papers, training, and emergency response information.

A diamond-shaped warning sign placed on the outside of a vehicle carrying hazardous materials. It identifies the hazard class and warns emergency responders and the public of the danger.

The document that describes hazardous cargo, including proper shipping name, class, quantity, and emergency contact. It must be kept where the driver can reach it and given to responders after a crash.

One of nine categories that group hazardous materials by the type of danger, such as explosives, flammable liquids, or corrosives. The class determines placarding, packaging, and handling rules.

A reference carried by hazardous materials drivers that lists initial response steps and safe distances for incidents by material name or placard number. It is used by responders and drivers before detailed help arrives.

A vehicle used to carry students to and from school or school activities. It has special lighting, stop arms, and loading procedures that require extra care around children and traffic.

The swinging sign on the left side of a school bus that extends when students are loading or unloading. Traffic in both directions must stop unless separated by a physical median.

The area around a stopped school bus where students enter or exit. Drivers must stop at a safe distance, watch for children crossing, and never pass a bus with its lights flashing.

A systematic check of the vehicle before driving, covering tires, brakes, lights, fluids, coupling, and cargo. It is required by law and helps catch defects that could cause a breakdown or crash.

The physical circuit around the vehicle during a pre-trip inspection. The driver checks components in a set order so nothing is missed, then verifies lights and signals from the driver's seat.

A check that the brakes work properly before driving. It includes testing the parking brake, checking air pressure buildup and leakage on air brake vehicles, and confirming the service brakes stop the vehicle straight.

The core driving skills of starting, steering, shifting, backing, and stopping smoothly. Good control means using gentle inputs, correct speed, and constant awareness of the vehicle's size and weight.

Moving the vehicle in reverse, which is the most dangerous routine maneuver because visibility is limited. Drivers should use mirrors, get out and check, and use a helper to guide them when possible.

A crash in which the vehicle tips onto its side or roof. It is often caused by taking a turn too fast, especially with a high center of gravity, and is among the most deadly large-truck crashes.