MA CDL General Knowledge key terms

A systematic check of a commercial vehicle's critical parts, performed before driving, to confirm it is safe and legally roadworthy. Drivers must document defects and refuse to operate an unsafe vehicle.

A written record of any defect found during inspection that affects safe operation. It must be completed and signed, and the carrier must act on it before the vehicle is dispatched again.

A stationary check confirming air pressure loss stays within limits with the engine off and brakes applied. Excessive loss signals a leak that makes the braking system unsafe to drive.

A buzzer and light that activate when air pressure drops below roughly 60 psi, warning that braking power is failing. Drivers must stop and diagnose before continuing.

Parking and emergency brakes held applied by heavy springs and released by air pressure. They apply automatically when air pressure falls too low, stopping the vehicle.

The lever linking a brake chamber pushrod to the brake shoe. Its travel distance must fall within limits; too much travel means brakes are out of adjustment and unsafe.

Setting flat and convex mirrors so the driver can see both sides and the rear of the vehicle with minimal overlap. Proper adjustment reduces blind spots before any backing maneuver.

An area around the truck that cannot be seen in the mirrors. Large vehicles have wide blind spots, especially on the right side and directly behind, so drivers must check carefully.

A danger area around a large vehicle where other drivers disappear from the trucker's view. Passing or tailgating in a no-zone risks a collision during turns or lane changes.

Get Out And Look: exiting the cab to inspect the area behind and around the vehicle before backing. It is the most reliable way to prevent backing collisions.

A person outside the vehicle who guides a backing driver using agreed hand signals. The driver must stop immediately if the spotter is lost from view.

A hazard created when a truck swings wide to turn right and a car moves into the open space on the right. The truck can crush the car against the curb.

The tendency of the rear wheels of a long vehicle to follow a tighter path than the front wheels during a turn. Drivers must swing wide and watch the trailer's path.

Steering toward the opposite side before a turn so the rear wheels clear the curb or obstacle. It must be done without entering another lane or striking nearby objects.

Shifting technique using two clutch presses per gear change, one to leave the gear and one to enter it, matching engine and transmission speed. It protects non-synchronized heavy-duty transmissions.

Shifting without using the clutch by matching engine speed to the next gear. It requires skill and is used with non-synchronized transmissions; done poorly it damages gears.

A technique of upshifting at progressively higher engine speeds to improve fuel economy and performance. It is used in modern trucks with electronic engines.

Revolutions per minute of the engine. Drivers watch the tachometer to shift within the engine's efficient range and avoid lugging or over-revving.

Operating the engine at too low an RPM under load, causing it to strain, overheat, or stall. Downshifting before the engine struggles prevents lugging and mechanical damage.

The space kept behind the vehicle ahead, measured in seconds by counting after it passes a fixed point. At least one second per ten feet of vehicle length is required.

The safety margin around a vehicle on all sides. Drivers should maintain it by adjusting speed, changing lanes, and avoiding clusters of traffic.

The total distance to stop, combining perception distance, reaction distance, and braking distance. It grows with speed, weight, and poor road conditions.

Loss of braking power from overheating brakes, common on long downgrades. Drivers prevent it by gearing down and using engine braking instead of riding the brakes.

Using a lower gear so the engine's compression slows the vehicle on a downgrade. It reduces reliance on wheel brakes and helps prevent overheating and fade.

An emergency escape lane with deep gravel or sand that stops a vehicle whose brakes have failed on a steep grade. Signs warn drivers well in advance.

Restoring control after wheels lose traction: release the brakes, steer where you want to go, and avoid sudden inputs. Skids are caused by overbraking, oversteering, or excessive speed.

A combination vehicle folding sharply at the articulation point, often from locked trailer brakes or abrupt steering. Correcting requires releasing the brakes and steering to straighten the rig.

Wheels riding on a layer of water and losing contact with the road, causing loss of steering and braking. It is prevented by reducing speed in heavy rain.

A lever in the cab that applies only the trailer brakes, used to test trailer braking and to help straighten a jackknife. It is not a parking brake.

The skill of scanning ahead and recognizing developing risks early, such as merging traffic or a stopped vehicle. It allows smooth speed and lane adjustments instead of sudden reactions.

An intersection of road and train tracks requiring drivers to slow, look, and listen before proceeding. Commercial vehicles carrying certain hazardous cargo must stop at every crossing.

A railroad crossing equipped with warning devices such as flashing lights, bells, or gates. Drivers must obey the signals and never attempt to beat a lowering gate.

A railroad crossing marked only by signs or pavement markings, with no electronic warning. The driver must stop, look, and listen before crossing.

The use of tiedowns, straps, and blocking to keep loads from shifting or falling. Federal rules set minimum tie-down counts and working load limits based on cargo weight.

The maximum load a tiedown or securement device is rated to hold safely. Summed WLLs must meet or exceed required percentages of the cargo weight.

Spreading cargo weight properly over axles so no axle is overloaded and steering and braking stay effective. It also means keeping the center of gravity low.

Federal limits on driving and on-duty time for commercial drivers, including the 11-hour driving and 14-hour on-duty windows. They are designed to prevent fatigue-related crashes.

Electronic logging device: equipment that automatically records driving time and duty status. Drivers must use it and keep records available for inspection.

Periods when a driver is relieved of work responsibilities and may rest. Sufficient off-duty time is required between shifts to reset driving limits.

Legal safeguards preventing a carrier from retaliating against a driver who reports safety violations or refuses to drive an unsafe vehicle. Complaints go to the federal regulator.

A directive from an inspector that a driver or vehicle may not operate because of serious violations. Driving in violation of the order carries substantial penalties.

An additional authorization added to a commercial license for specific vehicle types or cargo, such as air brakes, hazardous materials, or multiple trailers. Each requires separate testing.

The endorsement required to haul placarded amounts of hazardous materials. It involves a background check and knowledge testing on handling and emergency response.

The category of commercial license based on vehicle weight and configuration, such as Class A combinations or Class B heavy single vehicles. Class determines what may be driven.

Proof of a current DOT physical exam showing the driver meets health standards. Commercial drivers must keep it current and carry it or have it on file.