MN CDL General Knowledge key terms

A systematic check of lights, tires, brakes, coupling devices, and cargo before driving, required by federal rules. It catches defects that could cause a crash and is documented in a written report.

The maximum allowable pushrod travel for a given brake chamber size and type before the brake is out of adjustment and must be repaired. Exceeding it reduces stopping power and places the vehicle out of service.

A buzzer and light that activate when air tank pressure drops below roughly 60 psi, warning of insufficient air for braking. The driver must stop safely and find the leak before continuing.

The least legal tread depth for commercial vehicle tires, commonly 4/32 inch on front steering tires and 2/32 inch on other positions. Worn tread raises hydroplaning and blowout risk.

The combination of tiedowns, straps, chains, binders, and anchor points that holds cargo to the vehicle. It must meet working load limits and resist forward, rearward, and lateral forces.

The sum of the working load limits of all tiedowns used on a cargo section. Rules require this total to equal at least half the cargo weight, with a minimum number of tiedowns.

Movement of cargo during driving caused by inadequate securement or sudden maneuvers. It can change axle loading, damage the trailer, or push the vehicle out of its lane.

The point where the vehicle's weight is balanced. A high or off-center load raises this point, making rollover more likely during turns and evasive steering.

The maximum weight a single axle or axle group may carry under federal bridge formula and state law. Overloading an axle reduces steering and braking control and brings fines.

The lateral acceleration at which a vehicle tips over, often expressed in g's. Tall, heavily loaded trucks have a low threshold, so speed must be reduced well before curves.

The tendency of the rear wheels of a long vehicle to follow a tighter path than the front wheels in a turn. Drivers must swing wide and check mirrors to avoid hitting curbs or adjacent lanes.

Positioning the vehicle to the left of the lane or into an adjacent lane before a right turn so the trailer clears the curb. It prevents the rear wheels from climbing the curb or striking pedestrians.

Get Out And Look: exiting the cab to inspect the path and clearance before completing a difficult backing maneuver. It is the surest way to avoid unseen obstacles and pedestrians.

A person positioned to guide a driver during backing, using agreed hand signals. The driver must stop immediately if the spotter is lost from view in the mirrors.

A shifting technique for non-synchronized manual transmissions: press the clutch, shift to neutral, release the clutch, then press it again to engage the next gear. It matches gear speeds and reduces grinding.

Shifting without using the clutch by matching engine and transmission speeds. It saves clutch wear but requires skill and is not appropriate for every transmission or driver.

A fuel-saving technique of upshifting at lower engine rpm, often used in heavy trucks. It reduces wear and fuel use but must stay within the engine's torque range.

A guideline that a CMV should stay at least one second per ten feet of vehicle length behind the vehicle ahead, plus extra time in poor conditions. It provides room to stop.

The total distance traveled from the moment a hazard appears until the vehicle stops, combining perception, reaction, and braking distance. Speed and weight greatly increase it.

The buffer of empty space kept around the vehicle on all sides so there is room to react to other drivers. It is maintained by adjusting speed and lane position.

An engine compression brake that slows the vehicle without using the service brakes, helping control speed on downgrades. Many municipalities restrict its use because of noise.

Loss of braking power caused by overheating of brake drums or pads during prolonged or repeated use. Downshifting and controlled speed on grades prevent it.

A technique of applying the brakes firmly then releasing them repeatedly to slow a vehicle, used when brakes are wet or fading. It is not the same as anti-lock brake operation.

The actions taken to regain control when wheels lose traction: ease off the accelerator, steer in the direction the vehicle should go, and avoid hard braking. Panic inputs worsen a skid.

A loss of control in which the tractor and trailer fold at an angle, often after drive wheels lock or the trailer pushes the tractor. It can block the road and cause rollover.

Loss of tire contact with the road because a layer of water lifts the tire. Steering and braking become ineffective until speed drops and the tires regain contact.

A system that rapidly releases and reapplies brake pressure to prevent wheel lockup. Drivers should apply steady pressure and steer while the system works.

Federal limits on driving and on-duty time, including a maximum of 11 hours driving after 10 consecutive hours off duty and a 14-hour on-duty window. They are designed to prevent fatigue-related crashes.

An electronic system that records a driver's duty status and driving time automatically. It replaces paper logs and helps enforce hours-of-service rules.

A natural dip in alertness that typically occurs in the early morning and mid-afternoon hours. Drivers should plan breaks or rest during these periods to reduce crash risk.

Actions such as rest breaks, naps, caffeine, and good sleep habits that reduce drowsiness while driving. Rolling down a window or turning up music is not an effective remedy.

An intersection where a road crosses train tracks, marked by signs, lights, or gates. Drivers must slow, look both ways, and never stop on the tracks.

A situation in which a vehicle becomes stuck on a railroad crossing. The driver should get everyone out and away, then call the emergency number posted at the crossing.

A crossing warning that does not change, such as a crossbuck sign, pavement markings, or a stop sign. Drivers must rely on their own sight and hearing to detect trains.

The percentage of alcohol in a person's blood, used as the legal measure of impairment. Commercial drivers are held to a lower limit than other drivers and face serious penalties.

The legal principle that by driving, a person agrees to submit to alcohol or drug testing when lawfully requested. Refusal typically leads to license suspension and other penalties.

Alcohol or drug testing required when an employer has a belief based on specific observations that a driver is impaired. It is one of several testing categories under federal rules.

An area around the truck that the driver cannot see directly or in the mirrors. Large vehicles have big blind spots, so drivers must check mirrors and signal before lane changes.

The area alongside and behind a large vehicle where other drivers cannot be seen and where a truck's maneuver may surprise them. Sharing the road safely means staying out of it.

A road area where construction or maintenance is underway, often with narrowed lanes and reduced speed limits. Drivers should slow down, merge early, and watch for workers and equipment.

The skill of scanning ahead and recognizing developing risks, such as merging traffic, stopped vehicles, or changing signals, early enough to respond smoothly. It is central to defensive driving.