CDL general knowledge practice test
30 questions straight from federal rules, and 24 right clears the federal 80 percent bar. Each answer is tied to the rule it tests. No signup, no email.
30 questions, 45 minutes. The timer starts when you begin, and answers are shown at the end.
How the real New York exam is graded
New York DMV grades the written test on two conditions, and a paper has to meet both: at least 14 of the 20 questions right, and at least 2 of the 4 road sign questions right. A score of 14 or more still fails if 3 of the 4 sign questions are wrong. The car exam simulator here holds you to both, drawing exactly 4 road sign questions into every 20 question sitting. Class M uses the same 20 and 14, which is what the motorcycle paper runs at; it has no drawn sign questions to apply the sign condition to, so it is marked on the overall count only. DMV publishes no time limit for the office test and no rule ending it early, so the allowance on each paper is ours.
This paper allows 45 minutes. That allowance is ours, not a federal rule, because no published limit exists for this test.
Every question in this New York cdl general knowledge, with answers
All 30 questions this paper draws from, each with the correct answer, why it is correct, and the federal regulation it was drafted against. The paper itself picks a randomized subset and shuffles the options, so reading the list through is review rather than a shortcut.
1. What score is required to pass a CDL knowledge test?
- 90 percent
- 70 percent
- 75 percent
- 80 percent (correct answer)
Answer: 80 percent. Federal regulation fixes the standard: a CDL applicant must correctly answer at least 80 percent of the questions. States may not set it lower.
Source: 49 CFR 383.135(a)(1)
2. What blood alcohol concentration disqualifies a commercial driver?
- 0.04 or higher (correct answer)
- 0.02 or higher
- Any detectable amount
- 0.08 or higher
Answer: 0.04 or higher. The commercial threshold is 0.04, half the ordinary limit. A driver at or above it while operating a commercial vehicle is disqualified, and refusing a test carries the same consequence.
Source: 49 CFR 383.51 and 392.5
3. A commercial driver must not operate a vehicle within how many hours of consuming alcohol?
- 2 hours
- 4 hours (correct answer)
- 8 hours
- 1 hour
Answer: 4 hours. Federal rules bar operating a commercial vehicle within four hours of drinking alcohol, and bar possessing alcohol in the vehicle unless it is part of a manifested load.
Source: 49 CFR Part 392, driving of commercial motor vehicles
4. When must a commercial driver inspect their vehicle?
- Only when a fault is suspected
- Before the trip only
- Before, during and after the trip (correct answer)
- Only once a week
Answer: Before, during and after the trip. Federal rules require a pre-trip inspection, en-route checks during the journey, and a post-trip inspection with a written report of any defect that would affect safety.
Source: 49 CFR 392.7 and 396.11
5. The most important reason for a pre-trip inspection is:
- To record mileage
- To satisfy the insurer
- It is required paperwork
- To find problems that could cause a crash or a breakdown (correct answer)
Answer: To find problems that could cause a crash or a breakdown. The inspection exists to catch a failure before it becomes a crash. A defect found in a yard is an inconvenience; the same defect found at highway speed is not.
Source: 49 CFR Part 383, federal commercial driver standards
6. During a pre-trip inspection you find a cracked leaf spring. You should:
- Not drive the vehicle until it is repaired (correct answer)
- Drive only below 40 mph
- Report it at the end of the trip
- Note it and drive carefully
Answer: Not drive the vehicle until it is repaired. A cracked or broken leaf spring is an out-of-service condition. Suspension defects are among the items that make a vehicle unsafe to operate at all, not merely something to note.
Source: 49 CFR 396, out-of-service criteria
7. How does an empty truck stop compared to a loaded one?
- Always in a shorter distance
- Often in a longer distance, because there is less traction (correct answer)
- Exactly the same
- It depends only on speed
Answer: Often in a longer distance, because there is less traction. This surprises people. An empty truck has less weight pressing its tires onto the road, so it has less traction and its brakes and suspension are designed for a load. Empty rigs can take longer to stop.
Source: FMCSA commercial vehicle braking guidance
8. Total stopping distance for a large vehicle includes an element cars do not have. It is:
- Gear change delay
- Steering lag
- Brake lag, the time before the brakes take hold (correct answer)
- Load shift time
Answer: Brake lag, the time before the brakes take hold. Air brakes need time for air to travel and apply, commonly adding around half a second before braking begins. That lag is added to perception and reaction distance on top of the braking distance itself.
Source: FMCSA air brake guidance
9. The safe following distance rule for a commercial vehicle under 40 mph is:
- Two seconds regardless of length
- Three seconds regardless of length
- Half a second per 10 feet
- One second per 10 feet of vehicle length (correct answer)
Answer: One second per 10 feet of vehicle length. Allow one second for every 10 feet of vehicle length below 40 mph, then add a second above 40 mph. A 60 foot combination therefore needs six seconds, and seven above 40.
Source: FMCSA space management guidance
10. When backing a commercial vehicle you should:
- Back quickly to reduce exposure
- Get out and look, then back slowly using the driver side where possible (correct answer)
- Rely on mirrors alone
- Back toward the passenger side for better visibility
Answer: Get out and look, then back slowly using the driver side where possible. Walk the path before you move, back slowly, and prefer driver-side backing because you can see the rear along your own side. Passenger-side backing puts the whole maneuver in a blind area.
Source: FMCSA backing guidance
11. You are descending a long steep grade. The correct technique is:
- Use only the trailer brakes
- Use the brakes continuously to hold speed
- Select a low gear before the descent and use brakes intermittently (correct answer)
- Coast in neutral to save fuel
Answer: Select a low gear before the descent and use brakes intermittently. Choose the gear before you start down: the engine and driveline do most of the work. Riding the brakes overheats them and causes fade, and coasting in neutral is both unsafe and unlawful.
Source: FMCSA mountain driving guidance
12. Why should you avoid changing gear while going through a curve in a large vehicle?
- It is prohibited by regulation
- It damages the transmission
- It uses more fuel
- It can upset traction and stability just when you need them (correct answer)
Answer: It can upset traction and stability just when you need them. Shifting mid-curve interrupts drive to the wheels and can unsettle a heavy vehicle at exactly the wrong moment. Slow and select the gear before you enter.
Source: FMCSA vehicle control guidance
13. How far ahead should a commercial driver be looking?
- About 12 to 15 seconds ahead (correct answer)
- As far as the headlights reach
- To the vehicle in front
- About 4 seconds ahead
Answer: About 12 to 15 seconds ahead. Twelve to fifteen seconds is roughly a quarter mile at highway speed and a block in town. Looking only at the vehicle ahead removes all the warning you would otherwise get.
Source: FMCSA CDL model manual, seeing hazards
14. The largest blind spot around a tractor-trailer is:
- Along the left side
- Along the right side (correct answer)
- Directly behind
- Directly in front
Answer: Along the right side. The right side blind spot extends across multiple lanes and is the largest of the four. This is why right turns and right lane changes need the most caution and the most mirror work.
Source: FMCSA No-Zone guidance
15. Mirrors on a commercial vehicle should be checked:
- Once every few minutes
- Only before a lane change
- Regularly, roughly every 5 to 8 seconds (correct answer)
- Only at intersections
Answer: Regularly, roughly every 5 to 8 seconds. Frequent, brief mirror checks keep you aware of traffic settling into your blind spots and let you spot a tire fire, an open door or a shifting load before someone else does.
Source: FMCSA vehicle control guidance
16. Black ice is most likely to catch a commercial driver on:
- Uphill grades
- Well-lit urban roads
- Long open straights
- Bridges and overpasses (correct answer)
Answer: Bridges and overpasses. A bridge deck loses heat from above and below, so it freezes while the road either side is merely wet. Shaded stretches behave the same way.
Source: FMCSA winter driving guidance
17. Your drive wheels begin to skid. You should:
- Stop braking, push in the clutch and steer into the skid (correct answer)
- Accelerate to straighten the vehicle
- Apply the trailer brake only
- Brake harder
Answer: Stop braking, push in the clutch and steer into the skid. Release the brakes to let the wheels roll again, disengage drive so the engine is not pushing them, and steer where you want the front to go. Then counter-steer as it comes back in line.
Source: FMCSA skid control guidance
18. A trailer begins to swing out in a jackknife. Your first action is:
- Brake hard immediately
- Release the brakes to regain traction and straighten out (correct answer)
- Steer sharply the opposite way
- Apply the parking brake
Answer: Release the brakes to regain traction and straighten out. A trailer skid usually starts with locked trailer wheels. Releasing the brakes lets them roll and grip again, which is what allows the trailer to fall back into line behind the tractor.
Source: FMCSA skid control guidance
19. You have a tire fire. You should NOT:
- Use a fire extinguisher rated for the fire type
- Pull over and shut off the engine
- Use water on an electrical or fuel fire (correct answer)
- Call for help
Answer: Use water on an electrical or fuel fire. Water spreads a fuel fire and conducts electricity, so it is wrong for both. Match the extinguisher to the fire, stay upwind, and do not open a trailer door if you suspect fire inside.
Source: FMCSA emergency procedures guidance
20. A front tire blows out at speed. You should:
- Hold the steering wheel firmly, stay off the brakes, then slow gradually (correct answer)
- Steer onto the shoulder at once
- Accelerate to keep the vehicle straight
- Brake immediately and firmly
Answer: Hold the steering wheel firmly, stay off the brakes, then slow gradually. A front blowout pulls hard toward the failed tire and braking makes the pull worse. Grip the wheel, come off the throttle, let speed fall, then ease to the shoulder.
Source: FMCSA emergency procedures guidance
21. After stopping on the shoulder in an emergency, warning devices must be placed within:
- 5 minutes
- 10 minutes (correct answer)
- 20 minutes
- 30 minutes
Answer: 10 minutes. Federal rules require warning devices to be placed within ten minutes of stopping, positioned according to the road type, including a device well back on a divided highway.
Source: 49 CFR 392.22
22. A commercial driver convicted of a serious traffic violation in their own car:
- Must retake the knowledge test
- Faces no CDL consequence
- Can still be disqualified from holding a CDL (correct answer)
- Only faces a fine
Answer: Can still be disqualified from holding a CDL. CDL disqualification can follow from conduct in any vehicle. A driving-under-the-influence conviction in a private car disqualifies the commercial license just as it would in a truck.
Source: 49 CFR 383.51
23. A commercial driver must notify their employer of a traffic conviction within:
- 60 days
- 90 days
- 24 hours
- 30 days (correct answer)
Answer: 30 days. Convictions in any state and in any vehicle must be reported to the employer within 30 days, and a license suspension or revocation must be reported by the end of the next business day.
Source: 49 CFR 383.31 and 383.33
24. Which of these makes a driver subject to CDL requirements?
- A vehicle of 26,001 lb or more, or carrying 16 or more passengers, or placarded hazardous materials (correct answer)
- Any vehicle used for business
- Any vehicle towing a trailer
- Any vehicle over 10,000 lb
Answer: A vehicle of 26,001 lb or more, or carrying 16 or more passengers, or placarded hazardous materials. The federal definition covers a gross combination or vehicle weight rating of 26,001 lb or more, vehicles designed to carry 16 or more people including the driver, and any vehicle carrying hazardous materials requiring placards.
Source: 49 CFR 383.5, definition of commercial motor vehicle
25. At a railroad crossing, a driver carrying placarded hazardous materials must:
- Slow down but need not stop if clear
- Stop before the crossing, then proceed when safe (correct answer)
- Sound the horn and continue
- Cross only in low gear
Answer: Stop before the crossing, then proceed when safe. Placarded vehicles, buses carrying passengers and certain other vehicles must stop between 15 and 50 feet from the nearest rail, look and listen, and never change gear while crossing.
Source: 49 CFR 392.10
26. When a large vehicle turns right at a tight corner it should:
- Reverse to reposition
- Swing wide to the left first, then turn
- Turn wide as it completes the turn, keeping the rear close to the curb on entry (correct answer)
- Cross the center line to gain room
Answer: Turn wide as it completes the turn, keeping the rear close to the curb on entry. Swinging left first invites a car to fill the gap on your right, where the trailer finishes. Keep the rear of the vehicle close to the curb on entry and take the extra room on the way out.
Source: FMCSA turning guidance
27. Cargo on a commercial vehicle must be inspected:
- Only at the destination
- Only if the load shifts audibly
- Only before departure
- Within the first 50 miles, and again at intervals during the trip (correct answer)
Answer: Within the first 50 miles, and again at intervals during the trip. Federal rules require a check within the first 50 miles after loading, then again at intervals through the journey, because securement loosens as the load settles and the vehicle flexes.
Source: 49 CFR 392.9
28. In heavy rain at highway speed a commercial vehicle can hydroplane from around:
- 30 mph (correct answer)
- 55 mph
- 70 mph
- 15 mph
Answer: 30 mph. Hydroplaning can begin near 30 mph with standing water and worn tread, and does not need much depth. Reduce speed, avoid sudden inputs, and remember that low tread pressure raises the risk.
Source: FMCSA wet weather guidance
29. A driver feels drowsy on a long haul. The only real remedy is:
- Turning up the radio
- Stopping to sleep (correct answer)
- Opening a window
- Coffee and fresh air
Answer: Stopping to sleep. Caffeine and cold air mask fatigue briefly without restoring alertness, and a microsleep of a few seconds covers the length of a football field at highway speed. Only sleep fixes it.
Source: FMCSA hours of service and fatigue guidance
30. Which of these is a hazard you should expect from a parked car ahead?
- Reduced road width only
- Glare from its mirrors
- Nothing, parked cars are static
- A door opening or the vehicle pulling out (correct answer)
Answer: A door opening or the vehicle pulling out. Look for clues: exhaust smoke, wheels turned outward, brake lights, someone in the driver seat. A parked car is a hazard in waiting, and a large vehicle has neither the space nor the stopping distance to react late.
Source: FMCSA CDL model manual, seeing hazards
Other New York practice tests
Original practice questions written from the rules themselves, not the examination questions New York DMV uses. New York DMVneither runs this site nor endorses it.