Pennsylvania General Knowledge CDL Practice Test

This is a free 20-question practice test for the General Knowledge portion of the Pennsylvania Commercial Driver's License knowledge exam. Questions are pulled from a pool of 97 drawn from the AAMVA CDL Manual, which is the source document the Pennsylvania Department of Transportation Driver Licensing uses to write its actual exam.

How it works: Click an answer. The correct choice highlights in green, and you'll see a short explanation. Aim for 85% or better before you sit for the real test in Pennsylvania.

Question 1 of 20

Which lane is generally the best for a commercial vehicle on a multi-lane highway?

The far left (passing) lane
The middle lane
The right lane (slow lane)
Whichever has the lightest traffic

Correct. The right lane is generally best — it limits lane changes, reduces conflict with merging traffic only on the right, and matches commercial-vehicle speed.

Question 2 of 20

The most important reason for doing a vehicle inspection is to:

Comply with the law
Save fuel
Find safety problems before they cause a crash
Document mileage

Correct. A pre-trip inspection is meant to find problems that could cause a crash or breakdown. Compliance is a side effect, not the purpose.

Question 3 of 20

Which of the following is the best way to prevent a fire in your vehicle?

Carry extra fuel
Smoke only with the windows open
Inspect the vehicle, watch the gauges, and use safe driving practices
Run the engine hot to burn off carbon

Correct. Most fires are preventable through inspection (electrical, fuel-system, tire) and watching gauges, plus prohibiting smoking near fuel and observing safe loading/refueling rules.

Question 4 of 20

Which type of fire extinguisher should you use on an electrical fire?

Class A
Class B
Class C
Class D

Correct. Class B:C dry-chemical extinguishers (often labeled "B:C" or "ABC") are appropriate for electrical fires. Never use water on an electrical fire.

Question 5 of 20

Which of these is the best advice for staying alert on a long trip?

Drink coffee
Take cold pills
Get enough sleep before the trip and take rest breaks
Open the window

Correct. Adequate sleep before driving and scheduled rest breaks are the only reliable strategies. Coffee and cold air mask fatigue but do not eliminate it.

Question 6 of 20

Which of these is NOT a hazard you should look out for ahead?

Pedestrians
A vehicle stopped on the shoulder
Roadway construction
A clear, dry road

Correct. Hazards are conditions that could lead to a crash: pedestrians, stopped vehicles, work zones, debris. A clear, dry road is the absence of a hazard.

Question 7 of 20

When the engine is running in the cab inspection, you should check:

Oil pressure, ammeter/voltmeter, coolant temperature, engine oil temperature, and air pressure
Only the speedometer
Only the air-pressure gauge
Only the fuel gauge

Correct. After starting, watch the gauges to be sure all systems are operating normally before you drive.

Question 8 of 20

A fully loaded tractor-trailer traveling at 55 mph on dry pavement requires roughly what total stopping distance (perception + reaction + braking)?

100 feet
200 feet
300 feet (about the length of a football field)
600 feet

Correct. Total stopping distance for a heavy commercial vehicle at 55 mph on dry pavement is approximately 300 feet, or the length of a football field including end zones.

Question 9 of 20

A driver-side skid can cause a tractor-trailer to:

Drift gently
Jackknife
Improve steering
Over-correct only the trailer

Correct. When the drive wheels lose traction and the trailer continues forward, the tractor pivots and the rig jackknifes.

Question 10 of 20

Which of these statements about backing a heavy vehicle is true?

Backing is always safe if you go slow
Whenever possible, use a helper outside the vehicle to guide you
Always back from the right side because you can see better
Backing is the same as backing a car

Correct. Backing is always risky for heavy vehicles. Use a helper, communicate with hand signals agreed in advance, back slowly, and if alone, get out and look (G.O.A.L.).

Question 11 of 20

Hydroplaning is most likely to occur when:

Driving at low speed in light rain
Tires lose contact with the road and ride on water
Brakes are applied gently
Tires are over-inflated

Correct. Hydroplaning occurs when a film of water comes between the tires and the road, causing the tires to lose contact with the pavement. Higher speeds, worn tires, and standing water increase the risk.

Question 12 of 20

When a vehicle ahead of you brakes hard, you should:

Brake harder
Apply the brakes immediately, even if you don't need to
Look for a way to steer around the vehicle if necessary, while preparing to brake
Honk to warn the driver behind you

Correct. Plan your escape: identify a clear lane or shoulder. If you can steer to safety, you save reaction time. If not, brake firmly without locking the wheels.

Question 13 of 20

Most drivers who fall asleep at the wheel:

Are aware they are tired and pull over
Do not realize they are about to fall asleep
Have been drinking
Have been on the road less than an hour

Correct. Most drivers who fall asleep do not realize how drowsy they are. The only fix is to stop and rest before fatigue reaches that point.

Question 14 of 20

The "implied consent" rule means:

You agree to chemical testing for alcohol and drugs by holding a CDL and operating a commercial vehicle
Police need a warrant for any test
You may refuse all tests with no penalty
It applies only to passenger cars

Correct. By holding a CDL and operating a CMV on public roads, you have given implied consent to alcohol and drug testing. Refusing testing leads to disqualification just as a positive test does.

Question 15 of 20

Which of these is the best way to communicate that you are slowing down?

Tap the brake pedal a few times to flash the brake lights
Use the horn
Put on the parking brake
Wave at drivers behind

Correct. Lightly tapping the brake pedal flashes the brake lights, alerting drivers behind that you are slowing.

Question 16 of 20

When should you place reflective triangles on a divided highway after stopping due to a breakdown?

10, 50, and 100 feet behind the vehicle
10 feet to the rear, 100 feet to the rear, and 200 feet to the rear
10, 100, and 200 feet to the rear, on the traffic side
100, 200, and 500 feet to the rear

Correct. On a divided highway with traffic from one direction, place triangles 10, 100, and 200 feet behind the vehicle, on the shoulder or in the lane you stopped in.

Question 17 of 20

A vehicle's "no zone":

Refers to the lane next to the cab
Includes the front, sides, and rear blind spots where other vehicles disappear from view
Is the area in front of the truck only
Does not exist for cars

Correct. The "no zone" is the set of blind spots around a truck — front, both sides (especially right), and rear — where other vehicles cannot be seen.

Question 18 of 20

Federal regulations require a tie-down for every cargo, with a minimum of:

One tie-down for any cargo
One tie-down for items less than 5 feet long, two for items 5+ feet
At least one tie-down for each 10 feet of cargo, with minimums depending on length and weight
Tie-downs are not required for closed trailers

Correct. The general rule: at least one tie-down per 10 feet of article, plus a minimum based on length and weight (commonly two minimum for items over 5 feet or 1,100 lbs).

Question 19 of 20

Which is the safest stopping technique for a non-ABS vehicle whose brakes have started to lock up?

Continue braking hard until you stop
Stab braking: brake hard, release, brake hard again
Pump the brakes lightly
Coast in neutral

Correct. On a non-ABS vehicle, stab braking — full brake application until wheels lock, release, repeat — keeps the vehicle straight while still slowing.

Question 20 of 20

You should signal:

Only when other vehicles are visible
Continuously while driving
Well before any turn or lane change, and signal long enough to communicate
Only when changing lanes left

Correct. Signal early, signal long enough that other drivers see and process the signal, and cancel after the maneuver.

About the Pennsylvania General Knowledge exam

Most state DMVs administer 50 General Knowledge questions and require 80% (40 correct) to pass. Questions are pulled from a much larger pool, so two applicants taking the test on the same day will see different mixes. The questions on this site are drawn from the AAMVA CDL Manual chapters that every state's exam is built from.

The Pennsylvania Department of Transportation Driver Licensing follows the federal CDL standards established by FMCSA. To earn the General Knowledge credential, you must answer at least 80% of the questions correctly. Many candidates score lower the first time because the test pulls from a large pool — refreshing this page will give you a different mix of questions, drawn from the same authoritative source.

Want more practice? Try the full General Knowledge question bank or browse all Pennsylvania CDL practice tests.