CDL Combination Vehicles Test flashcards

The fifth wheel is a coupling device that connects a semi-trailer to a tractor. Proper coupling involves the kingpin locking securely into the fifth wheel jaws.

• Connects tractor to trailer.
• Kingpin must be fully engaged in locking jaws.
• Visual and tug test required for secure connection.
• Proper lubrication is important for operation.

Memory trick: Kingpin in, jaws tight, green light!

A test performed during a pre-trip inspection where the service brakes are applied and held to check for excessive air leakage. For a combination vehicle, the pressure drop should not exceed 4 psi in one minute.

• Tests the integrity of the entire brake system.
• Performed after full air pressure is built.
• Excessive drop indicates a leak requiring repair.

Memory trick: Four wheels on a combination vehicle, so 4 psi is the limit.

If a significant air leak is detected in a combination vehicle's air brake system, rendering the braking system unsafe, the vehicle must be immediately taken out of service.

• Constant compressor running signals a major leak.
• Loss of air pressure leads to brake failure.
• Safety is paramount; do not operate unsafe vehicles.

Memory trick: Leak + Constant Compressor = Stop, Repair, No More.

Steering wheel free play refers to the amount of turn allowed before the wheels begin to move. Excessive free play indicates wear or looseness in the steering components, compromising vehicle control.

• Should not exceed 2 inches on a 20-inch wheel.
• Indicates worn steering components.
• Affects vehicle control and safety.
• Check by gently turning steering wheel.

Memory trick: Too much play in the wheel means you're playing with danger.

Actions to take when service brakes become less effective due to overheating, to regain stopping power and control.

• Recognize signs of brake fade (less stopping power, burning smell).
• Downshift immediately to a lower gear.
• Use stab braking (firm, short applications) if service brakes still respond.
• Look for an escape ramp or safe runaway lane if available.

Memory trick: Fade means downshift, stab, and pray for an escape ramp.

On steep downgrades, use engine braking first. If speed still increases, use short, firm service brake applications to control speed and prevent brake fade.

• Engine braking is primary for downgrades.
• If insufficient, use 'stab braking' or controlled braking.
• Avoid continuous light braking to prevent overheating.

Memory trick: Downhill run, engine's done? Stab the brakes, have some fun!

The suspension system supports the vehicle and absorbs road shocks. Any major defect, especially in main components like leaf springs, can compromise safety and vehicle control.

• Includes springs, shock absorbers, hangers, U-bolts.
• Must be free of cracks, bends, or missing components.
• Main leaf spring cracks are critical defects.
• Ensures stability and comfort.

Memory trick: A cracked spring brings a cracking halt to your trip.

In construction zones, constantly monitor side clearances and be prepared to drive below the posted speed limit due to narrow lanes and barriers.

• Combination vehicles need extra space.
• Speed limits are maximums, not minimums.
• Focus on side clearances and adaptable speed.

Memory trick: Narrow Lanes, Nifty Lookouts, No Nasty Nudges.

When driving a combination vehicle in strong crosswinds, maintain a firm grip on the steering wheel and make small, continuous steering corrections to stay in your lane.

• Wind affects trailers more.
• Small, constant steering inputs.
• Reduce speed if necessary.

Memory trick: Wind blows? Grip tight, steer right (or left).

Spring brakes utilize powerful springs to apply the brakes when air pressure is lost or when manually activated, acting as both an emergency and parking brake.

• Engage automatically upon air pressure loss.
• Used for parking the vehicle.
• Are held off by air pressure during normal operation.

Memory trick: Springs are for Parking and Emergency stopping.

Excessive slack adjuster movement (e.g., >2 inches) indicates misadjusted brakes, requiring the vehicle to be taken out of service for repair by a qualified mechanic.

• Slack adjusters control brake shoe-to-drum distance.
• Excessive movement reduces braking force and causes uneven braking.
• A major safety defect requiring immediate repair.

Memory trick: Slack's too much, don't you touch! Out of service, that's the clutch!

Glad hands are connectors for the air lines between the tractor and trailer. Proper function requires them to be clean, free of corrosion, and to seal tightly.

• Connects tractor and trailer air lines.
• Must be clean and free of damage/corrosion.
• Ensures airtight seal for air brake system.
• Red (emergency) and blue (service) lines.

Memory trick: Glad hands must be happy, or the brakes will be sad.

The aggregate working load limit (WLL) of all tie-downs must be at least one-half (50%) of the weight of the cargo being secured.

• WLL is the maximum weight a component can safely hold.
• Applies to securing cargo against movement in all directions.
• Additional rules apply for specific cargo types (e.g., machinery, logs).

Memory trick: Half the weight, safe and sound, that's the WLL you've found!

The maximum allowable extension of the pushrod from a Type 30 brake chamber is 2 inches before the brake is considered out of adjustment.

• Indicates brake adjustment status
• Excessive travel reduces braking power
• Must be checked during pre-trip inspection

Memory trick: Remember 'Two for Type 30' to keep your brakes fine and dandy.

Air lines transmit compressed air for braking. Their integrity is paramount; any significant damage can lead to partial or complete brake failure.

• Service (blue) and emergency (red) lines.
• Must be free of cuts, chafing, and leaks.
• Coiled lines should not sag or rub.
• Damage can cause sudden air loss.

Memory trick: A chafed line is a ticking time bomb for your brakes.

The safest and most effective way for a commercial driver to manage drowsiness is to take a break and rest or nap at a safe location.

• Drowsiness impairs driving.
• Stimulants are temporary fixes.
• Rest is the only true solution.

Memory trick: Feeling sleepy? Pull over, be happy!

The maximum allowable movement of the brake pedal before resistance is felt, indicating that the brake system is beginning to engage.

• Ensures proper brake system response.
• Excessive free play reduces braking effectiveness.
• Must be checked during pre-trip inspection.

Memory trick: Two feet for two inches of play.

In case of air brake failure at highway speed, use engine braking, gently apply available trailer brakes, and seek a safe escape route.

• Do not pump brakes.
• Downshift for engine braking.
• Controlled trailer brake application.
• Seek escape ramp/shoulder.

Memory trick: No air? Downshift, hand brake, look for flare.

A jackknife occurs when the tractor and trailer fold in on each other, typically due to loss of traction. Prevention focuses on smooth, controlled driving.

• Avoid sudden braking, especially on slippery surfaces.
• Use engine braking (downshifting) to help slow down.
• Maintain a safe following distance.
• Be aware of road conditions and adjust speed accordingly.

Memory trick: Smooth moves keep the truck in a groove.

The pressure at which the air compressor governor stops the compressor from pumping air into the system, typically between 120 and 140 psi, to prevent over-pressurization and maintain system integrity.

• Normal range: 120-140 psi.
• Too low: insufficient air reserve.
• Too high: risk of component damage.
• Governed by the air compressor governor.

Memory trick: Governor Guides Gauge's Goal.

To detect air leaks, build system pressure to maximum, shut off the engine, apply the service brake, and monitor the air pressure gauges for drops.

• Pressure should not drop more than 3 psi in one minute for single vehicles.
• Pressure should not drop more than 4 psi in one minute for combination vehicles.
• Applying the service brake can reveal leaks in brake chambers or lines.

Memory trick: Pressure drops? Check the pipes and the seals!

A test performed with the engine off to verify that the low air pressure warning light and buzzer activate when air pressure drops to the specified threshold (typically 60 psi or above).

• Engine off, parking brakes off.
• Pump brake pedal to reduce pressure.
• Warning should activate at 60 psi or higher.

Memory trick: Engine off, brakes pump, watch for the warning, don't slump.

A pintle hook inspection ensures the coupling device used for drawbar trailers is free from defects that could compromise its ability to safely secure the trailer.

• Check for cracks, bends, or wear on the hook and associated parts.
• Ensure the locking mechanism operates freely and securely.
• Verify safety chains are properly attached and in good condition.

Memory trick: Pintle's plight? Cracks mean fright!

Inspecting the trailer's electrical connector (pigtail) ensures proper functioning of lights and ABS by checking for damage, corrosion, or frayed wires.

• Damaged wires can cause shorts or open circuits.
• Affects critical safety systems like lights and ABS.
• Must be securely connected and free from damage.

Memory trick: Frayed wires, no light; safety's plight!

If an automatic slack adjuster fails to maintain the correct pushrod stroke, allowing it to exceed legal limits, it indicates a malfunction that requires the vehicle to be taken out of service for inspection and repair, not manual adjustment.

• Automatic slack adjusters should self-adjust.
• Excessive stroke means a system defect.
• Manual adjustment is a band-aid for a broken auto-adjuster.

Memory trick: Auto-adjuster fails, 'Stop' the truck, 'Service' it now.

Unexpected tire overheating during a trip can point to underlying mechanical issues that require immediate attention to prevent tire failure or further damage.

• Common causes: underinflation, overloading, dragging brakes, bad bearings.
• Can lead to tire blowouts.
• Always check tire pressure and condition.
• Feel for excessive heat during inspections.

Memory trick: Hot tires tell tales of trouble in their bearings or brakes.

Combination vehicles require significantly more time and space to pass safely due to their length and slower acceleration. Ensure ample clear space before, during, and after the pass.

• More space needed.
• Slower acceleration.
• Check mirrors for entire passed vehicle before returning.

Memory trick: Longer Truck, Longer Look, Longer Room.

A hazard where the rear wheels of a long vehicle cut inside the path of the front wheels during a right turn, potentially striking objects or vehicles.

• Tractor-trailer combination requires more turning space.
• Rear wheels follow a shorter path than front wheels (off-tracking).
• Drivers must swing wide to the left before turning right.
• Check mirrors constantly to monitor trailer position.

Memory trick: Wide initial swing, prevent the squeeze sting.

A short trailer with a fifth wheel, designed to convert a semi-trailer into a full trailer. It allows a semi-trailer to be coupled behind another trailer, enabling double or triple trailer configurations.

• Has its own axle(s) and brakes.
• Equipped with a fifth wheel.
• Connects to the lead trailer with a pintle hook.
• Essential for double/triple trailer operations.

Memory trick: Dolly Doubles Drivers' Deliveries.

Sudden changes in motion cause cargo to shift due to inertia, significantly impacting a combination vehicle's stability and handling.

• Inertia resists changes in motion.
• Shifting cargo alters center of gravity.
• Proper securing prevents dangerous shifts.

Memory trick: Inertia's grip, cargo's slip, vehicle's tip.

In an emergency, apply firm, steady pressure to the service brakes of a combination vehicle to achieve maximum controlled stopping without locking the wheels.

• Avoid trailer hand brake for emergency stops.
• Steady pressure prevents wheel lock-up.
• Pumping air brakes is generally ineffective.

Memory trick: Sudden stop, firm brake, no wheel hop.

Immediate actions to safely manage a tire blowout in a combination vehicle to maintain control and stop safely.

• Hold steering wheel firmly.
• Stay off the brakes initially.
• Ease off the accelerator gradually.
• Steer straight ahead (counter-steer gently if needed).

Memory trick: Firm grip, no brake slip, let speed drip.

Pulling out the red trailer air supply knob removes air pressure from the trailer's emergency line, causing the trailer's spring (parking/emergency) brakes to apply.

• Controls trailer emergency/parking brakes.
• Push in to release, pull out to apply.
• A critical safety control.

Memory trick: Red knob out, trailer fixed to the ground, no doubt.

The air line, typically blue, that carries air from the tractor's foot valve or hand valve to the trailer's service brake chambers for normal braking.

• Connects to trailer service brakes.
• Controls normal braking on the trailer.
• A leak prevents service brake application.

Memory trick: Blue for service, red for emergency, keep them tight to stay free.

Proper cargo securement prevents movement during transit, ensuring vehicle stability, preventing damage to cargo, and protecting other road users.

• Cargo must be contained, immobilized, or secured.
• Use appropriate tie-downs, dunnage, and bracing.
• Check securement before, during, and after trips.
• Federal regulations (FMCSA) dictate securement standards.

Memory trick: Loose cargo makes for a loose driver.

A check valve in a dual air brake system is a one-way valve that isolates the primary and secondary air tanks, ensuring that a leak in one system does not deplete the air pressure from the other system.

• One-way air flow.
• Maintains system redundancy.
• Crucial for safety in case of air leak.

Memory trick: A check valve 'Checks' air flow, ensuring 'Safety' in a dual system.

Reduce speed before entering a curved off-ramp with a combination vehicle, then maintain a steady, controlled speed through the curve.

• Combination vehicles are prone to rollovers on curves.
• Brake before the curve, not in it.
• Maintain a steady, safe speed through the curve.

Memory trick: Slow before the Curve, Steady through the Turn.

When the low air pressure warning light and buzzer activate (typically below 60 psi), the driver must immediately stop driving and not move the vehicle until pressure returns to a safe operating range.

• Indicates insufficient braking pressure.
• Requires immediate stop.
• Do not move until pressure is safe.

Memory trick: Low air, light and buzzer, means stop, no fuss, no flutter.

Safely navigating curves in a combination vehicle requires reducing speed before entering the curve and maintaining a controlled speed throughout.

• Always heed advisory speed signs for curves.
• Brake before the curve, not in it.
• Accelerate gently out of the curve.

Memory trick: Curve's embrace, speed's slow dance, then a gentle pace.

When another vehicle merges too closely in front of a combination vehicle, gently reduce speed to re-establish a safe following distance.

• Combination vehicles need longer stopping distances.
• Aggressive reactions are unsafe.
• Prioritize creating space.

Memory trick: Close Car, Calmly Create Clearance.

A safety device in the air brake system, usually located on the first air tank, that automatically releases air pressure if it exceeds a predetermined safe limit (typically 150 psi) to prevent system damage.

• Protects air tanks and components from over-pressurization.
• Activates around 150 psi.
• Essential safety feature.

Memory trick: Safety Valve Saves System.

When encountering an object in the road, the priority is to maintain vehicle control. Gradually reduce speed, check for safe escape paths, and only change lanes if clear. If collision is unavoidable, aim to strike it at reduced speed.

• Avoid sudden maneuvers.
• Prioritize control.
• Reduce speed for impact if necessary.

Memory trick: Slow Down, Look Around, Decide, Act Smooth.

Rollovers in combination vehicles are primarily caused by driving too fast for conditions, especially in curves or turns, due to their high center of gravity.

• High center of gravity.
• Excessive speed in turns.
• Sudden steering inputs.

Memory trick: Slow down in curves to avoid a rollover.

A pre-trip inspection to check the free play or stroke of the slack adjusters on air brakes. Excessive movement (typically more than 1 inch) indicates that the brakes are out of adjustment and require immediate attention.

• Check by pulling on the slack adjuster by hand.
• Movement should not exceed 1 inch (or 3/4 inch, check local regs).
• Out of adjustment brakes are unsafe and must be corrected.

Memory trick: Slack Adjuster Stroke Shows Safety.

Hard braking with a combination vehicle on a slippery surface can lock trailer wheels, causing the trailer to swing out and lead to a dangerous jackknife.

• Slippery surfaces reduce traction.
• Hard braking locks wheels.
• Locked trailer wheels cause jackknife.

Memory trick: Slippery brake? Jackknife ache!

Any visible leakage of oil or grease from a wheel hub seal or axle end cap is a critical defect that requires immediate attention and repair before vehicle operation.

• Indicates a compromised seal.
• Can lead to lubricant loss and wheel bearing failure.
• Can contaminate brake components, reducing braking effectiveness.

Memory trick: Oil leak, don't ignore; fix it now, or risk much more!

The mechanism within the fifth wheel that closes around the trailer's kingpin to securely couple the trailer to the tractor.

• Must be fully closed and locked for safe operation.
• Open jaws indicate an unsecured coupling.
• Failure to lock can lead to trailer detachment.

Memory trick: Jaws must bite, or the trailer takes flight!

A significant difference in air pressure between the tractor and trailer (lower in the trailer) indicates an air leak in the trailer's system, requiring immediate inspection.

• Tractor and trailer pressures should equalize.
• Lower trailer pressure suggests a leak.
• Leaks compromise braking effectiveness.

Memory trick: Low trailer air? Check for a leak, beware!

The most effective method for stopping a combination vehicle quickly and safely in an emergency, maximizing braking force without losing control.

• Apply firm, steady pressure to the service brake pedal.
• Avoid locking the wheels to maintain steering control.
• Release and reapply brakes if wheels begin to lock (if not equipped with ABS).

Memory trick: STOP! Smooth, Steady, Safe

When passing with a combination vehicle, ensure ample clear space ahead to complete the maneuver safely due to the vehicle's extended length.

• Combination vehicles require longer passing distances.
• Check for oncoming traffic and sufficient space to return to lane.
• Do not cut off the vehicle being passed.

Memory trick: Long truck, long pass, check the road, make it last.

Driving safely through construction zones involves reducing speed, increasing following distance, and staying alert for changing conditions.

• Reduced speed limits are common.
• Lanes may be narrow or shift.
• Increased potential for unexpected stops or hazards.

Memory trick: Construction zones demand caution, not speed.

The landing gear supports the trailer when it is uncoupled from the tractor. Its proper functioning, including the crank handle, is essential for safe coupling and uncoupling.

• Must be fully raised and secured for travel.
• Crank handle must be functional and stowed.
• Check for bent, cracked, or damaged legs.
• Ensures stability when trailer is detached.

Memory trick: A bent handle means a bent plan for your next stop.

When driving in fog, reduce speed, use low beam headlights and fog lights, and increase your following distance to ensure safety and visibility.

• Low beams/fog lights only.
• Reduce speed.
• Increase following distance.

Memory trick: Slow, Low, and Far to Go.

The minimum safe following distance for a combination vehicle is calculated based on vehicle length and speed, typically requiring more time than passenger vehicles.

• Rule of thumb: 1 second per 10 feet of vehicle length.
• Add 1 second for speeds over 40 MPH.
• Increase distance in adverse conditions.

Memory trick: Ten feet, one second, then add one for speed, that's all you need.

Excessive trailer sway is most often caused by improper weight distribution, especially with too much weight loaded toward the rear of the trailer.

• Rear-heavy loads create a pendulum effect.
• Sway leads to instability and loss of control.
• Proper loading is crucial for stability.

Memory trick: Rear Weight Renders Rattle.

Regular inspection of the air compressor drive belt for damage (fraying, cracks, excessive wear) is crucial, as a failed belt will lead to loss of air pressure and braking capability.

• Inspect for fraying, cracks, and proper tension.
• Failure leads to loss of air pressure.
• Requires immediate replacement if damaged.

Memory trick: Frayed belt, no air, no brakes, beware!

When encountering ice, reduce speed significantly beforehand, avoid sudden inputs, and use a low gear to maintain control and prevent skids.

• Traction is severely reduced on ice.
• Sudden movements cause skids.
• Engine braking in a low gear helps control.

Memory trick: Ice Ahead? Idle, Input Gently, In Gear.

Actions taken to bring a trailer back into alignment when it starts to swing wide on a curve.

• Reduce speed by easing off the accelerator.
• Make small, gentle steering corrections.
• Avoid sudden braking or sharp steering.
• Anticipate curves and reduce speed before entering them.

Memory trick: Smooth and slow, let the trailer flow.

The distance a brake pushrod moves when the brakes are applied, indicating the adjustment status of the foundation brakes.

• Excessive travel means brakes are out of adjustment.
• Maximum travel limits vary by brake chamber type.
• Out-of-adjustment brakes reduce braking effectiveness.

Memory trick: Pushrod too far, brake's not there!

If a combination vehicle's service air pressure drops to 0 psi but the spring brakes fail to engage, it indicates a critical malfunction in the spring brake activation system, potentially the activation valve or related components, preventing automatic brake application.

• Spring brakes should apply automatically at low air pressure.
• Failure to apply is a severe safety defect.
• Points to a problem in the control or release mechanism.

Memory trick: No air, no park? The 'Activation Valve' is at fault, not delivering the final 'Signal'.