CDL Class A (General Knowledge) practice questions and exam guide

What does a leaking wheel seal indicate?

1. Cosmetic concern only
2. Need for tire rotation
3. Normal lubrication overflow
4. A defect that may put the vehicle out of service

Answer: D — A defect that may put the vehicle out of service

A) Off-by-one trap — drivers often dismiss seal leaks. D) Correct — an oil/grease leak from a wheel seal is a defect; can cause bearing failure or wheel-off. C) Not normal. B) Unrelated.

When checking the steering wheel for play, free play should not exceed approximately:

1. 10 degrees (about 2 inches on a 20-inch wheel)
2. 30 degrees
3. 45 degrees
4. 60 degrees

Answer: A — 10 degrees (about 2 inches on a 20-inch wheel)

A) Correct — about 10 degrees of free play is the limit; more indicates worn linkage. B/C/D) Excessive play indicates dangerous wear in steering components.

When parking and securing the vehicle, the proper procedure is:

1. Set parking brake first, then turn off engine
2. Turn off engine, then set parking brake
3. Use service brakes to hold; do not set parking brake
4. Leave engine running with parking brake set

Answer: A — Set parking brake first, then turn off engine

A) Correct — apply parking brake while engine still runs (so air pressure is full), then shut down. B) Less reliable. C) Service brakes leak. D) Wastes fuel and unsafe unattended.

If you start to hydroplane, your first action should be:

1. Brake hard
2. Steer sharply
3. Release the accelerator and avoid braking
4. Speed up

Answer: C — Release the accelerator and avoid braking

A) Braking can cause skid. B) Sharp steering loses control. C) Correct — release throttle, do not brake; the vehicle slows and tires regain contact. Use clutch on manual transmission. D) Increases hydroplane risk.

On a divided highway, the third warning triangle should be placed:

1. 10 feet behind the truck
2. Approximately 100 feet behind the truck
3. Approximately 200 feet behind the truck
4. Directly under the rear bumper

Answer: C — Approximately 200 feet behind the truck

A) Too close. B) That's the second triangle distance. C) Correct — on undivided road: 10/100/100 toward traffic. On divided/one-way: 10/100/200 feet behind. D) Useless placement.

The best remedy for fatigue is:

1. Coffee
2. Loud music
3. Sleep
4. Cold air on the face

Answer: C — Sleep

A) Temporary; wears off. B) Doesn't address fatigue. C) Correct — only sleep actually treats fatigue. D) Marginal at best. All other options just mask the problem.

High center of gravity increases the risk of:

1. Hydroplaning
2. Brake failure
3. Fuel inefficiency
4. Rollover, especially in curves

Answer: D — Rollover, especially in curves

A) Caused by water; not CG. D) Correct — high CG significantly raises rollover risk during cornering and emergency maneuvers. C) Indirect at best. B) Brakes fail from heat/wear, not CG.

A driver secures a stack of lumber with chains but the chain rubs over a sharp corner of the load. What is the BEST action?

1. Move the chain to a position where it crosses the load away from the corner
2. Loosen the chain slightly so that it does not press against the sharp corner
3. Place edge protection between the chain and the corner before tightening it
4. Replace the chain with a synthetic web strap that flexes around the corner

Answer: C — Place edge protection between the chain and the corner before tightening it

C) Correct — edge protection keeps the corner from cutting or crushing the tiedown and preserves its rated capacity. B) A loose tiedown lets the load move, which is a worse condition than a chafed one. A) Relocating may leave a section of the load unrestrained and does not address the corner. D) A web strap is even more vulnerable to a sharp corner than a chain is.

In a dual air brake system, what is the practical significance of having two separate circuits?

1. The parking brakes can be released without any air in the system at all
2. A failure in one circuit doubles the pressure available in the other
3. The compressor only has to charge one circuit at a time when running
4. A failure in one circuit still leaves braking on part of the vehicle

Answer: D — A failure in one circuit still leaves braking on part of the vehicle

D) Correct — separate circuits mean one failure does not leave the vehicle without brakes, though stopping distance will be longer. B) Pressure does not increase to compensate; only the surviving circuit's normal capacity remains. C) The compressor charges the whole system, and the split is about redundancy, not workload. A) Spring parking brakes specifically require air to release, so this reverses the design.

If the service brake air pressure suddenly drops while driving, you should:

1. Bring vehicle to a safe stop — spring brakes will engage at low pressure and may stop you abruptly
2. Pump brakes to build pressure
3. Continue at reduced speed
4. Use engine brake only

Answer: A — Bring vehicle to a safe stop — spring brakes will engage at low pressure and may stop you abruptly

B) Pumping wastes air. A) Correct — bring to controlled stop quickly; emergency spring brakes will engage at low pressure and could cause loss of control. C) Dangerous. D) Insufficient.

What does the tractor protection valve accomplish?

1. It keeps tractor air when the trailer separates
2. It boosts trailer air above tractor pressure
3. It locks the fifth wheel if the kingpin slips
4. It limits the trailer brakes on slick roads

Answer: A — It keeps tractor air when the trailer separates

A) Right — the valve closes to preserve tractor air if trailer air is lost, so the tractor keeps braking. B) It does not boost pressure anywhere. C) It has no mechanical role at the fifth wheel. D) Traction control on slick roads is a different system.

A driver enters an exit ramp posted for cars at a given speed with a loaded van trailer. What is the BEST practice?

1. Match the posted speed since it is legal there
2. Brake hard in the curve to shed extra speed
3. Accelerate through the curve to settle the load
4. Slow well below the posted figure before entering

Answer: D — Slow well below the posted figure before entering

D) Right — posted ramp speeds are set for cars, and a high-profile loaded truck must be slower before entering the curve. A) Matching the sign is the classic ramp rollover. B) Braking inside the curve unsettles the vehicle when it is least stable. C) Acceleration in the curve raises lateral force rather than settling anything.

A driver couples a converter dolly to the rear of the first trailer. What must be done with the dolly's safety chains?

1. They must be attached to the second trailer's landing gear support legs
2. They must be left hanging loose so they do not bind during sharp turns
3. They must be secured to the first trailer so the dolly cannot break free
4. They must be crossed under the dolly tongue and then hooked back to the dolly

Answer: C — They must be secured to the first trailer so the dolly cannot break free

C) Correct — the chains connect the dolly to the trailer ahead of it so a coupling failure does not release the dolly and the trailer behind it. B) Slack is needed for turning, but chains left unattached serve no purpose at all. A) Landing gear legs are not rated attachment points and would tear away under load. D) Hooking chains back to the dolly itself creates no connection to the towing vehicle.

In a doubles configuration, the heavier trailer should be:

1. In the rear
2. Always be empty
3. Doesn't matter
4. Directly behind the tractor (front)

Answer: D — Directly behind the tractor (front)

A) Causes whipping and instability. D) Correct — heavier trailer in front, lighter in rear, for stability. C) False. B) Misconception.

Smooth-bore tanks are typically used for:

1. Hazmat
2. All petroleum products
3. Gasoline only
4. Food products (milk, juice) where sanitation matters

Answer: D — Food products (milk, juice) where sanitation matters

A) Most hazmat uses baffled. D) Correct — food-grade tanks are smooth so they can be fully sanitized; this means driver must manage surge very carefully. C/B) Not specifically.

Liquid surge is most severe in:

1. Fully loaded tanks
2. Baffled tanks with full load
3. Empty tanks
4. Tanks that are partially loaded, especially smooth-bore (unbaffled) tanks

Answer: D — Tanks that are partially loaded, especially smooth-bore (unbaffled) tanks

A) Fully loaded means less surge. D) Correct — partial loads in smooth-bore tanks slosh dramatically, affecting handling. C) No liquid, no surge. B) Baffles reduce surge.

Which listing correctly pairs a class number with its family of materials?

1. Class 7 with radioactive material
2. Class 4 with corrosive liquids and acids
3. Class 6 with oxidizing agents
4. Class 8 with poisonous inhalation gases

Answer: A — Class 7 with radioactive material

A) Right — Class 7 is radioactive material. B) Class 4 covers flammable solids and water-reactive materials, not corrosives. C) Class 6 is poisons and infectious substances, not oxidizers. D) Class 8 is corrosives; poisons belong to Class 6.

If hazmat leaks during transport, you should:

1. Continue to the destination
2. Cover it with a tarp
3. Wash it off the road
4. Stop, isolate the area, notify emergency responders (911 + CHEMTREC), and do not try to clean it yourself

Answer: D — Stop, isolate the area, notify emergency responders (911 + CHEMTREC), and do not try to clean it yourself

A) Dangerous. D) Correct — secure the scene, notify authorities, refer to ERG, and let trained responders handle. C/B) Can spread contamination.

A bus stopped at a crossing sees the gates begin to rise after a train passes. What should the driver do NEXT?

1. Cross at once before the gate rises
2. Wait for a second train on the other track
3. Check for a second train, then cross
4. Shift to a lower gear once on the crossing

Answer: C — Check for a second train, then cross

C) Right — a second train on another track is a classic killer, so the driver confirms the crossing is clear and then crosses in a single gear. A) Starting under a moving gate risks contact with the arm. B) Waiting indefinitely for a train that may not exist blocks the crossing; the duty is to check. D) Shifting on the tracks risks losing motion.

What does the term danger zone mean around a school bus?

1. The lane behind the bus used by passing cars
2. The area around the bus where the driver cannot see
3. The zone inside the bus near the stepwell
4. The section of route with no shoulder available

Answer: B — The area around the bus where the driver cannot see

B) Right — the danger zone is the area on all sides of the bus where children are close enough to be struck and may be hidden from the driver's view. A) The passing lane is one hazard but not the definition. C) Interior areas are not the danger zone. D) Shoulder conditions describe the road, not the zone around the bus.

A medical card (DOT MCSA-5876) for CDL drivers is typically valid for:

1. 6 months
2. 1 year
3. Up to 24 months
4. 5 years

Answer: C — Up to 24 months

A) Too short. B) Possible if conditions warrant. C) Correct — up to 24 months for healthy drivers; shorter if monitored conditions. D) Too long.

Class A CDL covers:

1. Any combination ≥26,001 lbs with trailer ≥10,001 lbs
2. Any single vehicle ≥26,001 lbs
3. Vehicles transporting 16+ passengers
4. Hazmat only

Answer: A — Any combination ≥26,001 lbs with trailer ≥10,001 lbs

B) That's Class B. A) Correct — Class A is for combination vehicles with a tractor and trailer over the weight thresholds. C) Class B or C depending on weight. D) Hazmat is an endorsement, not a class.

What is the examiner evaluating during the on-road drive?

1. Only the ability to shift gears well
2. Turns, intersections and lane use
3. Only the applicant's speed control on grades
4. The applicant's knowledge of the local route

Answer: B — Turns, intersections and lane use

B) Right — the road test covers turns, intersections, lane changes, curves, grades, expressway driving and continuous traffic scanning. A) Shifting is one element among many. C) Grade handling is likewise only a portion. D) Route familiarity is not tested; the examiner gives directions.

The CDL skills test is conducted in how many parts, and in what general order?

1. Two parts, road test then written knowledge
2. Three parts, pre-trip, basic control, on-road
3. Three parts, on-road, pre-trip, then backing
4. Four parts, including a separate air brake road test

Answer: B — Three parts, pre-trip, basic control, on-road

B) Right — the skills test is the vehicle inspection, basic control skills and the on-road drive, generally in that order. A) The knowledge test precedes the skills test and is not part of it. C) The order is inverted; the inspection comes first. D) Air brakes are tested within the inspection, not as a fourth part.

Red 8-sided sign?

STOP.

What does CDL stand for?

Commercial Driver's License.

Name the three braking systems that make up a full air brake system.

The service brake system applied by the foot pedal • the parking brake system applied by the control valve • the emergency brake system that uses parts of both to stop the vehicle if air is lost.

Why do most truck rollovers happen, and what two loading and driving practices prevent them?

Rollovers occur when the driver takes a curve or ramp too fast for a high center of gravity. Keep the cargo mass as low as possible and centered, and slow to well below the posted ramp speed before entering the curve.

What items are prohibited from being carried in the aisle or stairwell of a passenger bus?

Baggage, freight, or any object that blocks the aisle, the driver's view, or the emergency exits; hazardous materials other than small-quantity exceptions are also prohibited on buses carrying passengers.

What is outage in tank loading and why is it necessary?

Outage is the empty space deliberately left in a tank so the liquid can expand as it warms. Without it, expansion can rupture the tank or force product out of the vents.