CDL
Commercial Driver's License, required to operate large commercial vehicles.
Getting Started: Understanding the CDL General Knowledge Test
Free knowledge base
CDL General Knowledge Test — key terms, tricks & tips
Everything from the course in one searchable place: 217 entries. Use it to review before a practice test or look up a word you forgot.
217 results
General Knowledge Test
Written exam covering basic commercial driving safety and regulations.
Getting Started: Understanding the CDL General Knowledge Test
CLP
Commercial Learner's Permit, allows supervised practice driving.
Getting Started: Understanding the CDL General Knowledge Test
Pre-trip Inspection
Thorough check of a vehicle before driving to ensure it's safe.
Getting Started: Understanding the CDL General Knowledge Test
Hours of Service (HOS)
Federal regulations limiting driving time for commercial drivers.
Getting Started: Understanding the CDL General Knowledge Test
Endorsements
Special certifications added to a CDL for specific vehicle types or cargo.
Getting Started: Understanding the CDL General Knowledge Test
Air Brakes
Common braking system in commercial vehicles, requiring special knowledge.
Getting Started: Understanding the CDL General Knowledge Test
Hazardous Materials (HazMat)
Substances posing risk to health, safety, or property, requiring special handling.
Getting Started: Understanding the CDL General Knowledge Test
What is the CDL General Knowledge Test?
To remember key test areas: 'S.V.B.C.R.' — Safe driving, Vehicle inspection, Basic control, Communication, Regulations.
Getting Started: Understanding the CDL General Knowledge Test
What is the CDL General Knowledge Test?
The California CDL General Knowledge Test includes questions specific to California vehicle codes and road signs, in addition to federal regulations. Pay close attention to sections on weight limits and specific lane use laws for commercial vehicles in California.
Getting Started: Understanding the CDL General Knowledge Test
What is the CDL General Knowledge Test?
Underestimating the breadth of topics covered, leading to insufficient study.
Getting Started: Understanding the CDL General Knowledge Test
What is the CDL General Knowledge Test?
Focusing only on memorization without understanding the 'why' behind the rules.
Getting Started: Understanding the CDL General Knowledge Test
What is the CDL General Knowledge Test?
Not reviewing state-specific information in addition to the federal manual.
Getting Started: Understanding the CDL General Knowledge Test
Multiple-choice
Questions with several options, choose the best one.
Getting Started: Understanding the CDL General Knowledge Test
Passing score
Minimum percentage (80%) required to pass the test.
Getting Started: Understanding the CDL General Knowledge Test
Endorsement tests
Additional tests for specific vehicle types or cargo.
Getting Started: Understanding the CDL General Knowledge Test
Retake policy
Rules for reattempting a failed CDL test section.
Getting Started: Understanding the CDL General Knowledge Test
Time management
Strategically allocating time during the exam.
Getting Started: Understanding the CDL General Knowledge Test
Computer-based test
Exam administered on a computer at a testing facility.
Getting Started: Understanding the CDL General Knowledge Test
Test Format and Scoring
For '80% to pass, don't be slow, read all options and let your knowledge flow!'
Getting Started: Understanding the CDL General Knowledge Test
Test Format and Scoring
The California CDL General Knowledge Test is typically 50 questions long. You must answer at least 40 questions correctly to pass (80%). If you fail, you must wait at least one day before retesting.
Getting Started: Understanding the CDL General Knowledge Test
Test Format and Scoring
Not reading all answer choices before selecting one, leading to choosing a 'good' answer instead of the 'best' answer.
Getting Started: Understanding the CDL General Knowledge Test
Test Format and Scoring
Rushing through the test and making careless errors due to lack of focus.
Getting Started: Understanding the CDL General Knowledge Test
Test Format and Scoring
Not understanding the passing score and miscalculating if they passed or failed.
Getting Started: Understanding the CDL General Knowledge Test
FMCSRs
Federal Motor Carrier Safety Regulations, governing CMV safety.
Driving Safely: Vehicle Control & Awareness
Steering play
Amount of steering wheel movement before wheels turn.
Driving Safely: Vehicle Control & Awareness
Air brake system
Braking system using compressed air for commercial vehicles.
Driving Safely: Vehicle Control & Awareness
Jackknifing
Trailer swings out at acute angle to tractor.
Driving Safely: Vehicle Control & Awareness
Engine power band
RPM range where engine produces most power.
Driving Safely: Vehicle Control & Awareness
Defect
Any fault or imperfection in a vehicle component.
Driving Safely: Vehicle Control & Awareness
Pre-Trip Inspection & Basic Vehicle Control
Remember 'T-CLOCS' for your walk-around: Tires, Controls, Lights, Oil, Chassis, Stands (or Suspension).
Driving Safely: Vehicle Control & Awareness
Pre-Trip Inspection & Basic Vehicle Control
The California CDL exam often emphasizes specific brake system checks, such as the air loss rate for air brakes (no more than 3 psi in one minute for single vehicles, 4 psi for combination vehicles) and the low air pressure warning signal (must come on before pressure drops to 55 psi).
Driving Safely: Vehicle Control & Awareness
Pre-Trip Inspection & Basic Vehicle Control
Skipping parts of the inspection due to being in a hurry, leading to missed defects.
Driving Safely: Vehicle Control & Awareness
Pre-Trip Inspection & Basic Vehicle Control
Not knowing the acceptable limits for component wear or fluid levels.
Driving Safely: Vehicle Control & Awareness
Pre-Trip Inspection & Basic Vehicle Control
Ignoring minor issues, thinking they can wait until after the trip.
Driving Safely: Vehicle Control & Awareness
Pre-Trip Inspection & Basic Vehicle Control
Failing to check under the hood for leaks or loose belts.
Driving Safely: Vehicle Control & Awareness
Engine Braking
Using the engine's resistance to slow the vehicle.
Driving Safely: Vehicle Control & Awareness
Brake Fade
Loss of braking power due to overheating.
Driving Safely: Vehicle Control & Awareness
Perception Distance
Distance traveled from seeing a hazard to recognizing it.
Driving Safely: Vehicle Control & Awareness
Reaction Distance
Distance traveled from recognizing to applying brakes.
Driving Safely: Vehicle Control & Awareness
Braking Distance
Distance traveled from brake application to full stop.
Driving Safely: Vehicle Control & Awareness
Total Stopping Distance
Sum of perception, reaction, and braking distances.
Driving Safely: Vehicle Control & Awareness
Following Distance
Space maintained between your vehicle and the one ahead.
Driving Safely: Vehicle Control & Awareness
Shifting Gears & Managing Speed and Space
P-R-B: 'Please Remember Brakes' for Perception, Reaction, and Braking distance, the three parts of Total Stopping Distance.
Driving Safely: Vehicle Control & Awareness
Shifting Gears & Managing Speed and Space
The California CDL exam emphasizes the '1 second per 10 feet of vehicle length' rule for following distance, adding an extra second above 40 mph. Be prepared to calculate this for various vehicle lengths and speeds, and remember to increase it for adverse conditions.
Driving Safely: Vehicle Control & Awareness
Shifting Gears & Managing Speed and Space
Not downshifting before a downgrade, leading to brake overheating.
Driving Safely: Vehicle Control & Awareness
Shifting Gears & Managing Speed and Space
Following too closely, especially in bad weather or with heavy loads.
Driving Safely: Vehicle Control & Awareness
Shifting Gears & Managing Speed and Space
Driving too fast for conditions, even if below the posted speed limit.
Driving Safely: Vehicle Control & Awareness
12-second rule
Looking 12-15 seconds ahead to anticipate hazards.
Driving Safely: Vehicle Control & Awareness
Hydroplaning
Tires losing contact with road due to water layer.
Driving Safely: Vehicle Control & Awareness
Black ice
Thin, invisible layer of ice, very dangerous.
Driving Safely: Vehicle Control & Awareness
Blind spot
Area around vehicle not visible in mirrors.
Driving Safely: Vehicle Control & Awareness
Low beams
Headlights for normal driving and adverse weather.
Driving Safely: Vehicle Control & Awareness
High beams
Brightest headlights, used only when no oncoming traffic.
Driving Safely: Vehicle Control & Awareness
Four-way flashers
Signals danger or a disabled vehicle.
Driving Safely: Vehicle Control & Awareness
Seeing, Communicating & Driving in Adverse Conditions
FOG: 'F'or 'O'utstanding 'G'uidance, use Low Beams and Go Slow!
Driving Safely: Vehicle Control & Awareness
Seeing, Communicating & Driving in Adverse Conditions
The California CDL exam frequently tests knowledge of safe driving in fog and rain. Remember to use low-beam headlights in fog and rain, and never use high beams in fog. Also, be prepared to explain the 12-second rule.
Driving Safely: Vehicle Control & Awareness
Seeing, Communicating & Driving in Adverse Conditions
Using high beams in fog, which reflects light back and worsens visibility.
Driving Safely: Vehicle Control & Awareness
Seeing, Communicating & Driving in Adverse Conditions
Not checking blind spots before changing lanes, leading to side-swipes.
Driving Safely: Vehicle Control & Awareness
Seeing, Communicating & Driving in Adverse Conditions
Driving at the same speed in adverse weather as in clear conditions, risking loss of control.
Driving Safely: Vehicle Control & Awareness
Escape Ramp
Runaway truck ramp for brake failure.
Driving Safely: Vehicle Control & Awareness
Railroad Crossing
Intersection of a road and railway tracks.
Driving Safely: Vehicle Control & Awareness
Blind Crossing
Crossing with obstructed view of tracks.
Driving Safely: Vehicle Control & Awareness
Downshift
Selecting a lower gear for more power/control.
Driving Safely: Vehicle Control & Awareness
Railroad Crossings, Mountain Driving & Emergencies
For railroad crossings, remember 'L.O.O.K.S.': Look, Open window, Observe, Know your stop, Safely cross.
Driving Safely: Vehicle Control & Awareness
Railroad Crossings, Mountain Driving & Emergencies
California law requires commercial vehicles carrying passengers or hazardous materials to stop between 15 and 50 feet from the nearest rail at all railroad crossings, even if no train is visible or gates are up, before proceeding safely.
Driving Safely: Vehicle Control & Awareness
Railroad Crossings, Mountain Driving & Emergencies
Trying to beat a train at a crossing, which is extremely dangerous and illegal.
Driving Safely: Vehicle Control & Awareness
Railroad Crossings, Mountain Driving & Emergencies
Riding the brakes continuously down a steep grade, leading to brake fade and potential failure.
Driving Safely: Vehicle Control & Awareness
Railroad Crossings, Mountain Driving & Emergencies
Not knowing the proper stopping distances for CMVs at railroad crossings.
Driving Safely: Vehicle Control & Awareness
Skid
Loss of tire traction with the road surface.
Driving Safely: Vehicle Control & Awareness
Counter-steer
Steering in the opposite direction of a skid to regain control.
Driving Safely: Vehicle Control & Awareness
Drive-wheel skid
Skid caused by loss of traction in the driving wheels.
Driving Safely: Vehicle Control & Awareness
Front-wheel skid
Skid caused by loss of traction in the steering wheels.
Driving Safely: Vehicle Control & Awareness
Warning devices
Triangles, flares, or reflective cones used to mark an accident scene.
Driving Safely: Vehicle Control & Awareness
Class A fire
Fires involving ordinary combustible materials.
Driving Safely: Vehicle Control & Awareness
Class B fire
Fires involving flammable liquids and gases.
Driving Safely: Vehicle Control & Awareness
Class C fire
Fires involving energized electrical equipment.
Driving Safely: Vehicle Control & Awareness
Skid Control, Accident Procedures & Fires
For Fire Extinguisher use, think PASS: Pull the pin, Aim at the base, Squeeze the handle, Sweep side to side.
Driving Safely: Vehicle Control & Awareness
Skid Control, Accident Procedures & Fires
The California CDL exam often asks about specific distances for placing warning devices after an accident. Memorize: within 10 feet of the front or rear, and 100 feet behind and ahead, or 10 feet, 100 feet, and 200 feet on a two-lane road or undivided highway.
Driving Safely: Vehicle Control & Awareness
Skid Control, Accident Procedures & Fires
Braking hard during a skid, which often worsens the skid.
Driving Safely: Vehicle Control & Awareness
Skid Control, Accident Procedures & Fires
Opening the hood of a vehicle with an engine fire, feeding oxygen to the flames.
Driving Safely: Vehicle Control & Awareness
Skid Control, Accident Procedures & Fires
Moving seriously injured accident victims unnecessarily, potentially causing more harm.
Driving Safely: Vehicle Control & Awareness
Fatigue
Extreme tiredness, resulting from mental or physical exertion or illness.
Driving Safely: Vehicle Control & Awareness
BAC (Blood Alcohol Concentration)
The percentage of alcohol in a person's bloodstream.
Driving Safely: Vehicle Control & Awareness
Distracted Driving
Any activity that diverts attention from the primary task of driving.
Driving Safely: Vehicle Control & Awareness
Aggressive Driving
Operating a vehicle in a selfish, bold, or pushy manner.
Driving Safely: Vehicle Control & Awareness
Placards
Diamond-shaped signs on vehicles indicating hazardous materials.
Driving Safely: Vehicle Control & Awareness
Endorsement
Special authorization added to a CDL to operate specific vehicles or carry certain cargo.
Driving Safely: Vehicle Control & Awareness
Shipping Papers
Documents identifying hazardous materials, their quantity, and emergency info.
Driving Safely: Vehicle Control & Awareness
Staying Alert, Fit to Drive & HazMat Basics
For 'Fit to Drive,' remember 'SAFE': **S**leep well, **A**void substances, **F**ocus always, **E**valuate health.
Driving Safely: Vehicle Control & Awareness
Staying Alert, Fit to Drive & HazMat Basics
California requires commercial drivers to adhere to strict hours-of-service regulations to prevent fatigue, which are often more stringent than federal rules for intrastate driving. Know the specific limits for driving and on-duty time in California.
Driving Safely: Vehicle Control & Awareness
Staying Alert, Fit to Drive & HazMat Basics
Believing coffee or energy drinks can replace sleep on a long haul.
Driving Safely: Vehicle Control & Awareness
Staying Alert, Fit to Drive & HazMat Basics
Ignoring early signs of fatigue and pushing through, leading to microsleeps.
Driving Safely: Vehicle Control & Awareness
Staying Alert, Fit to Drive & HazMat Basics
Assuming an over-the-counter medication is safe to take before driving without checking side effects.
Driving Safely: Vehicle Control & Awareness
Gross Vehicle Weight (GVW)
Total weight of vehicle and cargo.
Transporting Cargo Safely: Principles & Practices
Gross Combination Weight (GCW)
Total weight of powered unit and trailer(s).
Transporting Cargo Safely: Principles & Practices
Axle Weight
Weight transmitted to the road by an axle.
Transporting Cargo Safely: Principles & Practices
Center of Gravity (CG)
Point where vehicle's weight is concentrated.
Transporting Cargo Safely: Principles & Practices
Dunnage
Material used to support and protect cargo.
Transporting Cargo Safely: Principles & Practices
Blocking
Material used to prevent cargo movement.
Transporting Cargo Safely: Principles & Practices
Tie-downs
Devices used to secure cargo.
Transporting Cargo Safely: Principles & Practices
Cargo Inspection & Weight/Balance Fundamentals
W.A.S.H. - Weight, Axle, Shift, Height. Remember these factors for safe cargo!
Transporting Cargo Safely: Principles & Practices
Cargo Inspection & Weight/Balance Fundamentals
California's legal weight limits are generally consistent with federal standards, but specific routes or local ordinances may have stricter limits. Pay close attention to posted weight limits on bridges and roads, especially in urban areas or mountainous regions. The California Commercial Driver Handbook will detail any unique state-specific regulations.
Transporting Cargo Safely: Principles & Practices
Cargo Inspection & Weight/Balance Fundamentals
Failing to perform the initial 50-mile cargo inspection.
Transporting Cargo Safely: Principles & Practices
Cargo Inspection & Weight/Balance Fundamentals
Ignoring subtle signs of cargo shifting or loose tie-downs.
Transporting Cargo Safely: Principles & Practices
Cargo Inspection & Weight/Balance Fundamentals
Estimating weight and balance instead of using scales for heavy or critical loads.
Transporting Cargo Safely: Principles & Practices
Tiedown
Device (chain, strap) to secure cargo.
Transporting Cargo Safely: Principles & Practices
Bracing
Supports used to hold cargo in place.
Transporting Cargo Safely: Principles & Practices
WLL
Working Load Limit; max safe load for one tiedown.
Transporting Cargo Safely: Principles & Practices
AWLL
Aggregate WLL; sum of WLLs for all tiedowns.
Transporting Cargo Safely: Principles & Practices
Header Board
Front barrier protecting driver from cargo.
Transporting Cargo Safely: Principles & Practices
Securing Cargo: Techniques and Regulations
Think '5-1-10-1': 5 feet or less, 1 tiedown (if against bulkhead); for every 10 feet, 1 tiedown.
Transporting Cargo Safely: Principles & Practices
Securing Cargo: Techniques and Regulations
The California Commercial Driver Handbook emphasizes that all cargo must be contained, covered, or secured to prevent it from spilling, dropping, or shifting. Pay close attention to the requirement for tiedowns to be 'of sufficient strength' and that the combined working load limit of tiedowns must be at least one-half the weight of the cargo.
Transporting Cargo Safely: Principles & Practices
Securing Cargo: Techniques and Regulations
Using worn or damaged tiedowns, which can fail under stress.
Transporting Cargo Safely: Principles & Practices
Securing Cargo: Techniques and Regulations
Not checking tiedowns during a trip; they can loosen due to road vibration or cargo settling.
Transporting Cargo Safely: Principles & Practices
Securing Cargo: Techniques and Regulations
Underestimating the weight or forces acting on cargo, leading to insufficient tiedowns or WLL.
Transporting Cargo Safely: Principles & Practices
Slosh Effect
Side-to-side movement of liquid in a tank.
Transporting Cargo Safely: Principles & Practices
Surge Effect
Front-to-back movement of liquid in a tank.
Transporting Cargo Safely: Principles & Practices
Baffles
Internal tank dividers to reduce liquid movement.
Transporting Cargo Safely: Principles & Practices
Live Cargo
Transporting live animals, requiring special care.
Transporting Cargo Safely: Principles & Practices
Oversize Load
Cargo exceeding legal width, height, or length.
Transporting Cargo Safely: Principles & Practices
Overweight Load
Cargo exceeding legal weight limits.
Transporting Cargo Safely: Principles & Practices
Pilot Car
Escort vehicle for oversize loads, warning traffic.
Transporting Cargo Safely: Principles & Practices
Special Cargo: Liquids, Livestock, & Oversize Loads
L-L-O: Liquids, Livestock, Oversize. Remember these three L's and O's need extra care on the road!
Transporting Cargo Safely: Principles & Practices
Special Cargo: Liquids, Livestock, & Oversize Loads
California requires specific permits for oversize/overweight loads, often with stricter regulations on travel times (e.g., no travel during peak hours) and specific routes. The exam may ask about these permit requirements.
Transporting Cargo Safely: Principles & Practices
Special Cargo: Liquids, Livestock, & Oversize Loads
Driving a liquid tanker like a dry van, ignoring slosh/surge.
Transporting Cargo Safely: Principles & Practices
Special Cargo: Liquids, Livestock, & Oversize Loads
Not checking state-specific permit requirements for oversize loads.
Transporting Cargo Safely: Principles & Practices
Special Cargo: Liquids, Livestock, & Oversize Loads
Braking or accelerating too harshly with livestock onboard.
Transporting Cargo Safely: Principles & Practices
Tiedowns
Straps, chains, or ropes securing cargo by tension.
Transporting Cargo Safely: Principles & Practices
Center of Gravity
The point where an object's weight is balanced.
Transporting Cargo Safely: Principles & Practices
En-route Inspection
Re-checking cargo during the trip.
Transporting Cargo Safely: Principles & Practices
Cargo Safety Best Practices
C.A.R.G.O. S.A.F.E.: Check, Arrange, Restrain, Guard, Observe, Secure, Adjust, Fasten, Examine.
Transporting Cargo Safely: Principles & Practices
Cargo Safety Best Practices
The California CDL exam emphasizes the legal responsibility of the driver for cargo safety and the specific intervals for en-route inspections. Memorize the 'first 50 miles, then every 3 hours/150 miles' rule.
Transporting Cargo Safely: Principles & Practices
Cargo Safety Best Practices
Not checking cargo after the first 50 miles, assuming it's still secure.
Transporting Cargo Safely: Principles & Practices
Cargo Safety Best Practices
Overloading one axle to save space, leading to instability.
Transporting Cargo Safely: Principles & Practices
Cargo Safety Best Practices
Using damaged or insufficient tiedowns for the cargo weight.
Transporting Cargo Safely: Principles & Practices
Air Compressor
Pumps air into the air storage tanks.
Air Brakes: System Knowledge & Operation
Air Storage Tanks
Hold compressed air for the braking system.
Air Brakes: System Knowledge & Operation
Air Dryer
Removes moisture and oil from compressed air.
Air Brakes: System Knowledge & Operation
Governor
Controls when the air compressor pumps air.
Air Brakes: System Knowledge & Operation
Brake Pedal (Foot Valve)
Controls air flow to the brake chambers.
Air Brakes: System Knowledge & Operation
Brake Chambers
Convert air pressure into mechanical force.
Air Brakes: System Knowledge & Operation
Slack Adjuster
Adjusts brake lining wear automatically or manually.
Air Brakes: System Knowledge & Operation
S-Cam
Forces brake shoes against the drum.
Air Brakes: System Knowledge & Operation
Air Brake System Components
Compressors DRY Tanks, then Pedal sends air to Chambers, Adjusters, and S-Cams, making Brakes work!
Air Brakes: System Knowledge & Operation
Air Brake System Components
The California CDL exam often emphasizes the importance of draining air tanks daily and understanding the function of the air dryer. Pay close attention to questions about moisture removal and potential freezing.
Air Brakes: System Knowledge & Operation
Air Brake System Components
Forgetting to drain air tanks daily, leading to moisture buildup and system damage.
Air Brakes: System Knowledge & Operation
Air Brake System Components
Ignoring low air pressure warnings, which can lead to complete brake failure.
Air Brakes: System Knowledge & Operation
Air Brake System Components
Not understanding the difference between an air dryer and an alcohol evaporator.
Air Brakes: System Knowledge & Operation
Dual Air Brake System
Two separate air brake systems for safety.
Air Brakes: System Knowledge & Operation
Primary System
Typically controls the rear axle brakes.
Air Brakes: System Knowledge & Operation
Secondary System
Typically controls the front axle brakes.
Air Brakes: System Knowledge & Operation
Low Air Warning
Light/buzzer when pressure drops below 60 psi.
Air Brakes: System Knowledge & Operation
Air Leak Test
Checking for pressure drop over time.
Air Brakes: System Knowledge & Operation
Service Brake
Foot pedal brake for normal stopping.
Air Brakes: System Knowledge & Operation
Dual Air Brake Systems & Inspection
Dual means TWO. Two systems, two chances to stop!
Air Brakes: System Knowledge & Operation
Dual Air Brake Systems & Inspection
The California CDL exam often emphasizes the specific pressure at which the low air warning system must activate (typically 60 psi) and the maximum allowable air pressure drop during a leak test for both single and combination vehicles. Memorize these numbers precisely.
Air Brakes: System Knowledge & Operation
Dual Air Brake Systems & Inspection
Ignoring the low air pressure warning light or buzzer.
Air Brakes: System Knowledge & Operation
Dual Air Brake Systems & Inspection
Not performing a thorough air leak test during pre-trip inspection.
Air Brakes: System Knowledge & Operation
Dual Air Brake Systems & Inspection
Assuming the vehicle is safe to drive if only one brake system is working.
Air Brakes: System Knowledge & Operation
Snub Braking
Intermittent braking on downgrades to cool brakes.
Air Brakes: System Knowledge & Operation
Stab Braking
Applying and releasing brakes quickly in emergencies without ABS.
Air Brakes: System Knowledge & Operation
Parking Brake
Spring-activated brake for holding a parked vehicle.
Air Brakes: System Knowledge & Operation
Chock Wheels
Placing blocks against wheels to prevent movement.
Air Brakes: System Knowledge & Operation
Using Air Brakes Safely
For 'Snub Braking', remember: 'S-N-U-B: Slow, Not Until Below, Use Brakes'.
Air Brakes: System Knowledge & Operation
Using Air Brakes Safely
The California CDL exam often emphasizes mountain driving and runaway ramps. Memorize the 'snub braking' technique and the importance of selecting the correct gear before starting a downgrade.
Air Brakes: System Knowledge & Operation
Using Air Brakes Safely
Riding the brakes continuously on a downgrade, leading to overheating and brake fade.
Air Brakes: System Knowledge & Operation
Using Air Brakes Safely
Not selecting a low enough gear before starting a downgrade, forcing excessive brake use.
Air Brakes: System Knowledge & Operation
Using Air Brakes Safely
Failing to chock wheels when parking on a slope, even with the parking brake set.
Air Brakes: System Knowledge & Operation
Air Leak
Escape of compressed air from the system, causing pressure loss.
Air Brakes: System Knowledge & Operation
Compressor
Device that generates and maintains air pressure in the system.
Air Brakes: System Knowledge & Operation
Pushrod Travel
Distance the brake chamber pushrod moves when brakes are applied.
Air Brakes: System Knowledge & Operation
Cut-out Pressure
Pressure at which the air compressor stops pumping (around 125 psi).
Air Brakes: System Knowledge & Operation
Cut-in Pressure
Pressure at which the air compressor starts pumping (around 100 psi).
Air Brakes: System Knowledge & Operation
Air Brake System Troubleshooting
LEAKS: Listen, Examine, Act, Keep monitoring, Stop if critical.
Air Brakes: System Knowledge & Operation
Air Brake System Troubleshooting
The California CDL exam emphasizes the importance of pre-trip inspection for air brakes, including checking for air leaks and proper brake adjustment. Remember the specific air pressure drop rates: less than 2 psi in one minute for single vehicles, less than 3 psi for combination vehicles, and less than 3 psi in one minute with the engine off and brakes applied for single vehicles, less than 4 psi for combination vehicles.
Air Brakes: System Knowledge & Operation
Air Brake System Troubleshooting
Ignoring low air pressure warnings and continuing to drive.
Air Brakes: System Knowledge & Operation
Air Brake System Troubleshooting
Failing to check brake adjustment during pre-trip inspections.
Air Brakes: System Knowledge & Operation
Air Brake System Troubleshooting
Not draining air tanks regularly, leading to water contamination.
Air Brakes: System Knowledge & Operation
Jackknife
When a trailer swings out, forming an acute angle with the tractor.
Combination Vehicles: Driving & Maintenance
Rollover
When a vehicle tips over onto its side or roof.
Combination Vehicles: Driving & Maintenance
Off-tracking
Rear wheels of a combination vehicle follow a shorter path than front wheels.
Combination Vehicles: Driving & Maintenance
Articulation Point
The pivot point where a trailer connects to a tractor or another trailer.
Combination Vehicles: Driving & Maintenance
ABS
Anti-lock Braking System; prevents wheel lock-up during braking.
Combination Vehicles: Driving & Maintenance
Driving Combination Vehicles Safely
To remember rollover causes, think 'S.C.A.R.S.': Speed, Curves, A-frame (high center of gravity), Rollover risk, Sudden steering.
Combination Vehicles: Driving & Maintenance
Driving Combination Vehicles Safely
The California CDL exam often emphasizes specific speed limits for combination vehicles on certain highways and the legal requirements for brake adjustments. Be precise about the 55 mph speed limit for trucks with three or more axles or towing a trailer, and know that brake adjustment limits are critical for safety inspections.
Combination Vehicles: Driving & Maintenance
Driving Combination Vehicles Safely
Taking curves too fast, leading to rollovers.
Combination Vehicles: Driving & Maintenance
Driving Combination Vehicles Safely
Braking too hard or suddenly, especially on slippery surfaces, causing jackknifes.
Combination Vehicles: Driving & Maintenance
Driving Combination Vehicles Safely
Not allowing enough space for turns or stopping, underestimating the vehicle's size and weight.
Combination Vehicles: Driving & Maintenance
Fifth Wheel
Coupling device on tractor that connects to trailer's kingpin.
Combination Vehicles: Driving & Maintenance
Kingpin
Protruding pin on trailer that locks into fifth wheel jaws.
Combination Vehicles: Driving & Maintenance
Landing Gear
Retractable legs that support the front of a detached trailer.
Combination Vehicles: Driving & Maintenance
Glad Hands
Coupling devices for connecting air lines between tractor/trailer.
Combination Vehicles: Driving & Maintenance
Apron
Flat plate on the underside of the trailer that rests on fifth wheel.
Combination Vehicles: Driving & Maintenance
Tug Test
Gently pulling tractor forward to verify secure coupling.
Combination Vehicles: Driving & Maintenance
Chocks
Wedges placed to prevent trailer wheels from rolling.
Combination Vehicles: Driving & Maintenance
Coupling and Uncoupling Procedures
C-A-T-S: Connect, Air, Tug, Secure. A simple reminder for key coupling steps.
Combination Vehicles: Driving & Maintenance
Coupling and Uncoupling Procedures
For the California CDL exam, pay close attention to the specific steps for securing air and electrical lines, and the importance of ensuring the fifth wheel locking handle is fully engaged or disengaged. Keywords to spot include 'tug test,' 'landing gear,' and 'kingpin.'
Combination Vehicles: Driving & Maintenance
Coupling and Uncoupling Procedures
Not performing a tug test after coupling, leading to a dropped trailer.
Combination Vehicles: Driving & Maintenance
Coupling and Uncoupling Procedures
Forgetting to chock trailer wheels before uncoupling, allowing the trailer to roll.
Combination Vehicles: Driving & Maintenance
Coupling and Uncoupling Procedures
Not fully raising landing gear after coupling, causing damage during turns.
Combination Vehicles: Driving & Maintenance
Pintle Hook
Coupling device for converter dollies/trailers.
Combination Vehicles: Driving & Maintenance
Converter Dolly
Connects multiple trailers in a combination.
Combination Vehicles: Driving & Maintenance
Inspecting Combination Vehicles
Remember 'CALM' for your coupling check: C - Connections (air/electrical), A - Apron (flat), L - Locking (jaws/release arm), M - Mount (fifth wheel secure).
Combination Vehicles: Driving & Maintenance
Inspecting Combination Vehicles
California requires specific attention to brake adjustment. For air brakes, the pushrod travel must be within legal limits (e.g., typically no more than 2 inches for Type 30 chambers). Know these specific measurements for your exam.
Combination Vehicles: Driving & Maintenance
Inspecting Combination Vehicles
Overlooking small air leaks because they seem insignificant.
Combination Vehicles: Driving & Maintenance
Inspecting Combination Vehicles
Not checking the fifth wheel release arm for full engagement and security.
Combination Vehicles: Driving & Maintenance
Inspecting Combination Vehicles
Failing to inspect the underside of the trailer for frame damage or loose components.
Combination Vehicles: Driving & Maintenance
G.O.A.L.
Get Out And Look; a safety practice for backing.
Combination Vehicles: Driving & Maintenance
Blind spots
Areas around a vehicle not visible in mirrors.
Combination Vehicles: Driving & Maintenance
Swing wide
Maneuver to allow for off-tracking during turns.
Combination Vehicles: Driving & Maintenance
Combination vehicle
A truck-tractor pulling one or more trailers.
Combination Vehicles: Driving & Maintenance
Combination Vehicle Maneuvers
B.A.C.K. S.L.O.W. - Backing Always Cautiously, Keep Steering Little, Observe Widely.
Combination Vehicles: Driving & Maintenance
Combination Vehicle Maneuvers
The California CDL exam frequently asks about off-tracking and proper turning techniques for long vehicles. Pay close attention to questions regarding how much space is needed for turns and lane changes.
Combination Vehicles: Driving & Maintenance
Combination Vehicle Maneuvers
Not checking mirrors frequently enough during turns or lane changes.
Combination Vehicles: Driving & Maintenance
Combination Vehicle Maneuvers
Attempting to back a combination vehicle too quickly or without G.O.A.L.
Combination Vehicles: Driving & Maintenance
Combination Vehicle Maneuvers
Underestimating off-tracking, leading to hitting curbs or other objects.
Combination Vehicles: Driving & Maintenance