CDL General Knowledge Test flashcards

A critical safety component that automatically opens to release excessive air pressure in the air brake system.

• Acts as a backup if the air governor fails.
• Typically set to open around 150 psi.
• Prevents damage to air tanks and other components.

Memory trick: Safety Valve: High Pressure? No Stress, I'll Release the Mess!

The process of identifying sources of air loss in an air brake system, often indicated by audible hissing or a pressure drop.

• Leaks reduce braking effectiveness.
• Can be found using soapy water or listening.
• Requires immediate repair to ensure safety.

Memory trick: Hiss + Drop = Leak's Got a Job!

An air brake system with two separate air systems, each with its own air tank, lines, and controls, typically for front and rear brakes.

• Provides a backup in case of single system failure.
• Requires both systems to be fully charged.
• Enhances safety.

Memory trick: Dual tanks, dual thanks for safety.

The maximum allowable pushrod travel for most commercial vehicles with S-cam air brakes before adjustment is required is 2 inches.

• Measured with full brake application.
• Exceeding 2 inches is a critical defect.
• Shorter travel means more effective braking.
• Check all wheels.

Memory trick: Two inches (or 1 3/4) is the max, beyond that, your brakes are lax.

A condition in an air brake system where too much air escapes, often indicated by a large pressure drop when the service brakes are applied.

• Indicates leaks in the system.
• Can lead to brake failure.
• Requires immediate repair.

Memory trick: Pressure drops fast, leaks are vast.

A condition where brakes on one side of the vehicle apply with more or less force than the other side, causing the vehicle to pull.

• Can be caused by misadjusted brakes, faulty chambers, or contaminated linings.
• Dangerous, as it can lead to loss of control.
• Requires immediate inspection and repair.

Memory trick: Pulling = Unbalanced Brakes = Danger!

A test to verify that the air compressor can efficiently build and maintain sufficient air pressure in the air brake system.

• Performed at normal engine idle.
• Checks build time from 85 psi to 100 psi.
• Maximum time is typically 45 seconds for dual systems.

Memory trick: 85 to 100? 45 Seconds, Get It Done!

Material (such as wood, air bags, or foam) used in cargo securement to fill voids, cushion, and prevent cargo movement.

• Protects cargo from damage.
• Fills empty spaces to prevent shifting.
• Absorbs shock and vibration.
• Used in conjunction with other securement methods like tiedowns.

Memory trick: Dunnage fills the gaps, protects the goods, and stops the taps.

Federal regulations specify a minimum number of tiedowns for logs transported within bunks or cradles to ensure stability.

• Logs contained in bunks/cradles have some inherent stability.
• Minimum of two tiedowns required for any length of log load in bunks/cradles.
• Additional tiedowns may be needed based on length and weight.

Memory trick: Logs in their beds, two straps on their heads.

A manual valve (often a push-pull knob) that controls the flow of air to the spring brake chambers, engaging or releasing the parking brakes.

• Pushed in to release parking brakes (air supplied).
• Pulled out to apply parking brakes (air exhausted).
• A common point of failure for parking brake issues.

Memory trick: Valve Vexes Release: If the valve won't move, neither will the brake.

Securing cargo with a high center of gravity requires methods that prevent rollover by increasing stability and resisting lateral forces.

• Rollover is the primary risk for high center of gravity loads.
• Tiedowns should pull cargo downwards and outwards.
• Direct tiedowns are crucial for stability.

Memory trick: High loads need anchors pulling wide, not just from the top.

Immediate and safe shutdown of the vehicle's engine upon detecting significantly low oil pressure to prevent catastrophic engine damage.

• Low oil pressure indicates a lack of lubrication.
• Continued operation will lead to severe engine wear.
• Stopping the engine prevents further damage.

Memory trick: When the oil light glows, the engine's health goes.

Any oil leak from the differential, regardless of size, must be inspected and repaired by a qualified mechanic before operating the commercial vehicle.

• Indicates a potential mechanical issue.
• Can lead to component failure if ignored.
• Requires professional repair, not just monitoring or temporary fixes.

Memory trick: Don't just drive, inspect and fix, or your trip will be in a fix!

A condition where the air brake system loses air pressure too quickly when the service brakes are applied, often due to a significant leak.

• Indicated by rapid pressure drop on gauge.
• Low air warning light and buzzer activate quickly.
• Requires immediate attention and repair.

Memory trick: Rapid air loss means a big brake system flaw, requiring immediate attention.

Federal regulations dictate the minimum number of tiedowns based on cargo length and whether it is blocked against the front.

• One tiedown for every 10 feet of cargo length or fraction thereof.
• Minimum of two tiedowns always required.
• An additional tiedown is needed if the cargo is not blocked against the front.

Memory trick: Lengthy loads need lots of loops unless blocked.

Any unintended escape of compressed air from the air brake system, often indicated by a continuous pressure drop on the dashboard gauge, hissing sounds, or requiring the compressor to run excessively.

• Can be caused by loose fittings, damaged air lines, or faulty components.
• Reduces braking effectiveness and can lead to brake failure.
• Requires immediate attention and repair.

Memory trick: Leaky lines lead to low air levels, needing immediate intervention.

A safety procedure at railroad crossings where a commercial driver visually confirms the tracks are clear in both directions, looking left, then right, then left again, before proceeding.

• Ensures no second train is approaching.
• Prevents proceeding when a train is obscured or another is coming.
• Critical for CMV safety due to longer stopping distances and lower maneuverability.

Memory trick: Look left, then right, then left again, before you cross the train.

The speed at which the air compressor can increase air pressure in the reservoirs from a specified low pressure to a specified high pressure.

• For single vehicles, 85 to 100 psi in 45 seconds or less.
• For combination vehicles, 85 to 100 psi in 45 seconds or less (engine at operating RPM, parking brake off, service brake released).
• This test verifies compressor efficiency.

Memory trick: Compressor build-up: Fast enough to keep you safe, slow enough to be a problem.

Cargo that is stacked but not interlocked (e.g., empty barrels) requires more rigorous tiedown methods to prevent shifting and falling.

• Increased risk of instability due to stacking and lack of interlocking.
• Requires more tiedowns than single-layer or interlocked cargo.
• General rule: one tiedown per 10 feet of length, with additional tiedowns for layers.

Memory trick: Stacked but not stuck? Double up the straps for luck!