Free CDL Exam Flashcards

Class A permits operation of combination vehicles with a GCWR of 26,001+ lbs when the towed vehicle exceeds 10,000 lbs (tractor-trailers, tanker trucks). Class B covers single vehicles with a GVWR of 26,001+ lbs (straight trucks, buses). Class C applies to vehicles designed for 16+ passengers or transporting hazardous materials requiring placards.

Gross Vehicle Weight Rating (GVWR) is the maximum safe weight of a single vehicle including cargo, passengers, and fuel as determined by the manufacturer. Gross Combination Weight Rating (GCWR) is the maximum allowable weight of a power unit plus all towed units and their loads. Understanding these ratings is essential for determining which CDL class is required.

Under FMCSA regulations, drivers may drive a maximum of 11 hours after taking 10 consecutive hours off duty. This driving time limit is designed to prevent fatigue-related accidents. Once you reach 11 hours of driving, you must take another 10-hour off-duty period before driving again.

Drivers cannot drive beyond the 14th consecutive hour after coming on duty, following 10 consecutive hours off duty. This is a fixed window that cannot be extended with off-duty time. Even if you haven't driven the full 11 hours, once 14 hours have passed since coming on duty, you cannot drive until completing another 10-hour off-duty period.

FMCSA requires drivers to take a 30-minute break after 8 cumulative hours of driving time without at least a 30-minute interruption. This break can be satisfied by any non-driving period of 30 consecutive minutes, including on-duty not driving time, off-duty time, or sleeper berth time.

Drivers cannot drive after accumulating 60 hours on duty in 7 consecutive days, or 70 hours on duty in 8 consecutive days, depending on the carrier's operating schedule. A driver may restart this cycle by taking 34 or more consecutive hours off duty. This rule prevents excessive weekly driving hours.

Since February 2022, FMCSA requires all first-time CDL applicants to complete Entry-Level Driver Training from an approved training provider listed in the Training Provider Registry. The training includes both theory and behind-the-wheel instruction. Training providers must report successful completion to the FMCSA before students can take their skills test.

Before obtaining a CDL, you must hold a Commercial Learner's Permit for at least 14 days. The CLP requires passing the general knowledge test and any endorsement knowledge tests. While holding a CLP, you may only drive with a qualified CDL holder in the front seat who holds the proper CDL class and endorsements.

A vehicle must be placed out of service for critical safety violations discovered during inspections, such as brake defects affecting more than 20% of service brakes, steering wheel play exceeding limits, or fuel system leaks. Drivers can also be placed out of service for HOS violations, alcohol/drug use, or not having proper documentation.

At the end of each driving day, drivers must complete a DVIR documenting the vehicle's condition including brakes, steering, lights, tires, horn, and coupling devices. Any defects affecting safety must be reported. The carrier must repair items before dispatch, and the driver must sign the previous day's report acknowledging repairs were made.

The air brake system consists of an air compressor (builds pressure), governor (controls compressor), air reservoirs/tanks (store compressed air), brake chambers (convert air pressure to mechanical force), slack adjusters (transfer force to brake drums), and foundation brakes (drums, shoes, or disc components that create friction to stop the vehicle).

The air compressor is powered by the engine and pumps air into storage tanks. The governor controls when the compressor pumps air, typically cutting out at 120-145 psi and cutting in around 100 psi. The compressor must build air pressure from 85 to 100 psi within 45 seconds; slower build-up indicates a problem.

Air brakes have a lag time of about one-half second between pressing the brake pedal and when brakes activate. This is because air must travel through lines to reach the brakes. At 55 mph, your vehicle travels an additional 32 feet during this lag time. Always maintain extra following distance when driving vehicles with air brakes.

Total stopping distance equals perception distance plus reaction distance plus brake lag distance plus braking distance. At 55 mph on dry pavement, a loaded truck's total stopping distance can exceed 400 feet. Air brake vehicles require more stopping distance than hydraulic brake vehicles due to the additional brake lag time.

Spring brakes use powerful springs held back by air pressure during normal operation. When air pressure drops below approximately 20-30 psi, the springs apply the brakes automatically. This is a fail-safe design ensuring brakes apply if air pressure is lost. Never use the parking brake when brakes are very hot, as they may lock and damage drums.

Modern trucks have dual air brake systems with two separate air tanks feeding different sets of brakes. If one system fails, the other can still stop the vehicle. The primary system typically operates rear brakes, while the secondary system operates front brakes. A warning light or buzzer activates if either system loses pressure.

A low air pressure warning device must activate before air pressure drops below 60 psi. This warning is usually a red light and buzzer on the dashboard. If the warning comes on while driving, pull over safely and stop immediately. Continuing to drive with low air pressure can result in complete brake failure.

With a fully charged system (approximately 125 psi), turn off the engine and release the parking brake. After the initial pressure drop, the air pressure should not drop more than 2 psi in one minute for single vehicles, or 3 psi for combination vehicles. Greater drops indicate dangerous air leaks that must be repaired.

S-cam brakes are the most common type of foundation brake on commercial vehicles. When air pressure is applied, the brake chamber pushes a rod connected to the slack adjuster, which rotates an S-shaped cam. This cam forces the brake shoes outward against the brake drum, creating friction to slow or stop the vehicle.

Moisture in compressed air can freeze in cold weather, blocking brake lines. Some systems have alcohol evaporators that help reduce this risk by injecting alcohol into the air system. Regardless, air tanks must be drained daily to remove water and oil. Automatic tank drains are available but manual draining should still be performed.

The fifth wheel is the coupling device on a tractor that connects to a semi-trailer's kingpin. For proper coupling, the fifth wheel jaws must close securely around the kingpin shank with no space between the upper and lower fifth wheel plates. Always check that the locking lever is in the locked position and the safety latch is engaged.

To couple: 1) Inspect fifth wheel and kingpin, 2) Position trailer at proper height (slightly lower than fifth wheel), 3) Back tractor straight under trailer until fifth wheel engages kingpin, 4) Pull forward gently to test coupling, 5) Check visually that jaws are locked around kingpin, 6) Connect air lines and electrical cord, 7) Raise landing gear.

To uncouple: 1) Position on level ground, 2) Chock trailer wheels, 3) Lower landing gear until it touches ground firmly plus extra turns, 4) Disconnect air lines and electrical cord, store in dummy couplers, 5) Release fifth wheel locking mechanism, 6) Pull tractor forward slowly with trailer brakes locked, 7) Stop when frame clears trailer.

Glad hands are the coupling devices used to connect air lines between the tractor and trailer. The service line (blue) carries air to the trailer brake chambers, while the emergency/supply line (red) supplies air to the trailer air tanks. Always clean glad hands before connecting and ensure they are properly seated to prevent air leaks.

The trailer air supply control allows the driver to open and shut off air to the trailer. In emergency situations or if trailer air lines are disconnected, this valve protects the tractor's air supply. It automatically closes when air pressure drops to 20-45 psi, applying trailer spring brakes and protecting tractor air reserves.

A jackknife occurs when the drive wheels lose traction, causing the tractor to swing around toward the trailer. This typically happens during hard braking on slippery surfaces or when the trailer is empty. Prevention includes gradual braking, maintaining proper following distance, and slowing down before curves. Once a jackknife begins, release brakes immediately.

Trailer swing occurs when a trailer's rear wheels take a different path than the front wheels during turns, potentially hitting objects or pedestrians. Off-tracking means the trailer follows a shorter path than the tractor in turns. Allow extra space on the right side during right turns, and avoid turning too sharply.

Combination vehicles have a high center of gravity making them prone to rollover, especially when loaded. Key prevention measures include slowing down before curves and ramps, keeping cargo as low and balanced as possible, avoiding sudden steering movements, and being extra cautious with liquid tankers which can experience surge forces.

To obtain a HAZMAT endorsement, drivers must pass a written knowledge test covering hazardous materials transportation rules, complete a TSA background check (fingerprints and records check), and pay applicable fees (approximately $85 as of 2025). The endorsement must be renewed every five years. The endorsement is marked with an 'H' on the CDL.

A HAZMAT endorsement is required when transporting any quantity of hazardous material that requires placarding under 49 CFR 172, or any quantity of a select agent or toxin. If no placard is required (such as limited quantities under 1,001 pounds for Table 2 materials), no endorsement is needed. Class 9 materials don't require placards for domestic transport.

Placards are diamond-shaped signs (at least 10.75 inches square) placed on all four sides of a vehicle to identify the hazard class of cargo. They must be readable from all directions. Different colors and symbols indicate different hazard classes: red for flammable, yellow for oxidizer, white for poison, orange for explosive, etc.

The nine HAZMAT classes are: Class 1 (Explosives), Class 2 (Gases - flammable, non-flammable, poison), Class 3 (Flammable Liquids), Class 4 (Flammable Solids), Class 5 (Oxidizers and Organic Peroxides), Class 6 (Poisons and Infectious Substances), Class 7 (Radioactive Materials), Class 8 (Corrosives), and Class 9 (Miscellaneous Dangerous Goods).

Shipping papers must describe hazardous materials using the proper shipping name, hazard class, UN/NA identification number, and packing group. HAZMAT entries must be highlighted, listed first, or marked with an 'X' in the HM column. During transport, shipping papers must be within driver's reach or in the door pocket when driver is out of vehicle.

When loading or unloading hazardous materials: set parking brakes and chock wheels, turn off engine (unless needed for operation), prohibit smoking within 25 feet, never use hooks or other metal tools on containers, handle packages carefully, and follow specific loading requirements for each hazard class. Never open packages unless authorized.

In a HAZMAT emergency: keep people away from the scene, warn others of danger, contact emergency responders with shipping paper information, do not touch or inhale spilled materials, and remove injured persons only if safe to do so. The Emergency Response Guidebook (ERG) provides guidance for first responders handling incidents.

It is illegal to transport leaking packages, open containers of hazardous materials, or improperly labeled shipments. Drivers cannot smoke within 25 feet of a vehicle containing explosives or flammables. Parking near open flames or populated areas with certain HAZMAT is prohibited. Never transport incompatible materials together in the same vehicle.

A thorough pre-trip inspection is required by FMCSA regulations before operating a commercial motor vehicle. The purpose is to identify defects that could cause accidents or breakdowns, ensure the vehicle meets safety standards, and protect the driver from liability. Inspections typically take 15-20 minutes and should follow a consistent routine.

Check oil level (should be between add and full marks), coolant level in reservoir, power steering fluid level, and windshield washer fluid. Inspect belts for cracks, fraying, or looseness, and hoses for leaks or bulges. Look for fluid leaks underneath the engine. Check wiring for damage and ensure air compressor is properly mounted.

Inspect brake drums for cracks and excessive wear, brake shoes for proper thickness (at least 1/4 inch), and brake chambers for damage. Check air lines and hoses for cracks, wear, or leaks. Verify slack adjusters are properly adjusted (no more than 1 inch of movement on S-cam brakes). Test low pressure warning and spring brake operation.

Check tire pressure, tread depth (minimum 4/32 inch on steer tires, 2/32 inch on other tires), and condition. Look for cuts, bulges, tread separation, and dual tires touching. Verify lug nuts are present, tight, and not cracked or damaged. Check valve stems for damage. Front tires cannot be recapped, regrooved, or have less than 4/32 inch tread.

Check steering wheel for excessive free play (no more than 10 degrees or 2 inches movement on a 20-inch wheel before front tires begin to move). Inspect steering column, U-joints, gear box, and pitman arm for damage. Check power steering fluid level, hoses, and pump for leaks. Ensure all steering components are securely mounted.

Test all lights including headlights (high and low beam), turn signals, four-way flashers, brake lights, tail lights, clearance lights, and marker lights. Check for cracked or broken lenses. Verify reflectors are clean and in place. Test horn and windshield wipers/washers. Ensure all required lights are operational before night driving.

Check mirrors for proper adjustment and cleanliness, windshield for cracks or obstructions, seatbelt operation, and door latches. Verify required safety equipment is present: fire extinguisher (properly charged), warning triangles (3 required), and spare fuses. Check that all gauges are working and ELD or logging device is functional.

Commercial vehicles require greater following distances due to their weight and stopping distance. The general rule is one second per 10 feet of vehicle length, plus one additional second if traveling over 40 mph. For a 60-foot vehicle at highway speeds, maintain at least 7 seconds following distance. Double this in poor conditions.

Before descending a long or steep grade, reduce speed and shift to a lower gear that will allow you to control speed without excessive braking. Use engine braking (jake brake if equipped) as the primary slowing method. Apply brakes firmly enough to feel a definite slowdown, then release. Repeated light braking causes brake fade and failure.

Brake fade occurs when brakes overheat and lose their effectiveness. This happens from excessive or prolonged brake use, particularly on long downgrades. Symptoms include needing more pedal pressure to maintain speed and unusual brake smell. Prevention includes using proper gear selection and engine braking rather than relying solely on service brakes.

Hydroplaning occurs when tires lose contact with the road and ride on a layer of water. It can happen at speeds as low as 30 mph if there is enough water on the road. To recover, release the accelerator, do not brake, and allow the vehicle to slow naturally. Proper tire inflation and good tread depth reduce hydroplaning risk.

Most skids are caused by over-braking, over-steering, or over-accelerating. For a rear-wheel skid (most common), release the brakes or accelerator and steer in the direction you want to go. Do not steer sharply or brake hard during recovery. Counter-steer only as much as necessary and be ready to correct in the opposite direction.

Buses, vehicles carrying passengers for hire, and vehicles carrying certain hazardous materials must stop at all railroad crossings 15-50 feet from the nearest rail. Turn off all noise sources and open windows to listen for trains. Never shift gears while crossing tracks. If your vehicle stalls on tracks, get everyone out and away from the vehicle immediately.

In rain, reduce speed by one-third; in snow or ice, reduce by half or more. Turn on low beam headlights for visibility. Increase following distance significantly. Avoid sudden moves with steering, braking, or accelerating. If conditions become too dangerous, find a safe place to stop and wait. Never drive through deep water or onto flooded roadways.