CDL General Knowledge test: free practice drill and what it covers

The CDL General Knowledge test is the one every applicant takes, for every class: about 50 multiple-choice questions (40 correct to pass in Washington) on inspection, vehicle control, seeing and communicating, space and speed, hazards, emergencies, cargo, and alcohol and fatigue. The free drill below is 12 original questions with every answer explained.

50
questions on the real test: 40
correct to pass (80%): All
classes take it: 12
questions in the free drill

Last checked 20 October 2026 · Counts from the Washington State Department of Licensing; pass mark from 49 CFR 383.135

Free General Knowledge drill: 12 original CDL-style questions at a practice pace of a minute a question, then every answer explained. No sign-up.

12
questions
12 min
time limit
Free
every answer explained

By the LifeScore Editorial Team · Updated 20 October 2026 · How we check facts · How this is scored

What is on the CDL General Knowledge test?

Everything in the general sections of your state CDL manual: how to inspect a vehicle, control it, see and be seen, manage space and speed, handle hazards, night, winter and mountain driving, skids, emergencies, crashes and fires, and how to load and secure cargo.

The main topics, in the order most manuals teach them
Topic	What the questions ask
Vehicle inspection	The seven-step inspection, what counts as a defect on tires, brakes, steering and lights
Basic control and shifting	Starting, backing safely, double clutching, when to downshift
Seeing and communicating	How far ahead to look, mirrors, signals, horn and flashers
Space and speed	Following distance, stopping distance, speed on curves and grades
Hazards	Spotting hazardous drivers and road conditions, work zones, railroad crossings
Night, winter and mountain driving	Headlights and glare, chains, black ice, choosing gears for downgrades
Emergencies and skids	Steering to avoid a crash, brake failure, tire blowouts, skid recovery
Crashes and fires	Warning devices, fire classes and extinguishers
Alcohol, drugs and fatigue	The 0.04 and 4-hour rules, disqualification, staying alert
Cargo	Securement, weight limits, check intervals, hazardous materials basics

Because General Knowledge is so broad, it is usually the test people pass by the smallest margin. Fifty questions at 80% means ten misses is the limit, and the misses cluster in the same few places: the numbers, skids and emergencies, and the inspection.

What numbers are on the General Knowledge test?

Following distance, stopping distance at 55 mph, tread depth, the warning triangle distances, the cargo check intervals and the alcohol rules; learn these and you remove the questions most people guess on.

General Knowledge numbers, with where each comes from
Rule	Number	Source
Following distance	1 second per 10 feet of vehicle length below 40 mph; add 1 second above 40 mph	State CDL manual
Stopping at 55 mph (dry)	About 142 ft perception + 61 ft reaction + 216 ft braking = 419 ft; air brakes add about 32 ft of lag	State CDL manual
Tread depth	At least 4/32 inch on front (steering) tires, 2/32 inch on all others	49 CFR 393.75
Warning triangles, two-way road	Within 10 ft of the vehicle, then about 100 ft behind and 100 ft ahead	State CDL manual
Warning triangles, divided or one-way road	10 ft, 100 ft and 200 ft behind, toward approaching traffic	State CDL manual
Cargo checks	Within the first 50 miles, then every 3 hours or 150 miles, whichever comes first	State CDL manual
Alcohol	None within 4 hours of duty; 0.04 is DUI in a CMV; any detectable amount means 24 hours out of service	49 CFR 392.5; state CDL manual
Spring brakes / tractor protection valve	Come on, or close, between 20 and 45 psi	State CDL manual, air brakes and combinations
Leakage, engine off	Released: under 2 psi a minute (single), 3 (combination). Applied: under 3 (single), 4 (combination)	State CDL manual, air brakes

Two of these are calculations the test likes to set. Following distance: divide your length by 10 for the seconds, then add one second above 40 mph, so a 60-foot rig at 55 mph needs 7 seconds. Stopping distance: braking distance grows with the square of speed, so doubling your speed makes it about four times as long, not twice.

Feet per second is the link between them. Multiply miles per hour by about 1.47: at 55 mph you cover about 81 feet every second, which is why a one-second lapse in attention costs almost the length of a tractor-trailer.

What do CDL General Knowledge questions look like?

Short questions on a rule or a driving situation, with four options. Three examples follow; the first is worked in full and the others open when you tap.

CDL-style question 1 · Following distance
You are driving a 70-foot combination at 50 mph on a dry road. By the CDL manual's rule, at least how many seconds should you leave between you and the vehicle ahead?
1. A7 seconds
2. B8 seconds
3. C5 seconds
4. D10 seconds
Worked answer
B: 8 seconds. One second for each 10 feet of length is 7 seconds, and you add 1 second because you are above 40 mph: 8 seconds.
1. Length: 70 ÷ 10 = 7 seconds.
2. Speed is over 40 mph, so add 1 second.
3. 7 + 1 = 8 seconds.
The trap: Stopping at 7. The extra second above 40 mph is the part of the rule people forget.
CDL-style question 2 · Hazards
You stop on the shoulder of a two-lane road with traffic both ways. Where should your three warning triangles go?
1. AAll three behind you, 10, 100 and 200 feet back
2. BOne within 10 feet of the vehicle on the traffic side, one about 100 feet behind and one about 100 feet ahead
3. COne beside each front tire and one at the rear
4. DOne 500 feet behind you and two at the vehicle
Show the worked answer
B: One within 10 feet of the vehicle on the traffic side, one about 100 feet behind and one about 100 feet ahead. On a two-way road, traffic can come from either side, so you protect both directions: one by the vehicle, one about 100 feet behind and one about 100 feet ahead.
1. Ask which way traffic comes from: both ways on a two-lane road.
2. So you need a triangle ahead as well as behind.
3. Pattern: within 10 feet, then about 100 feet in each direction.
The trap: The 10-100-200 pattern is for one-way or divided roads, where all traffic comes from behind.
CDL-style question 3 · Tires
During your pre-trip inspection, a front (steering) tire has 3/32 inch of tread in its major grooves. What should you do?
1. ADrive; 2/32 inch is the minimum
2. BDrive; any visible tread is legal
3. CDo not drive; front tires need at least 4/32 inch
4. DDo not drive; every tire needs at least 6/32 inch
Show the worked answer
C: Do not drive; front tires need at least 4/32 inch. Federal rules (49 CFR 393.75) require at least 4/32 inch on front tires and 2/32 inch on the others. 3/32 is below the front-tire minimum.
1. Find the tire position: front (steering).
2. Front minimum: 4/32 inch. Others: 2/32 inch.
3. 3/32 is under 4/32, so the tire must be replaced before driving.
The trap: Using the 2/32 rule for every tire. The steering tires get the stricter limit because a front blowout is the hardest to control.

Make General Knowledge your safest test

Four General Knowledge drills and eight full mocks, every answer explained from the manual.

The CDL Pass Pack gives you 8 full mocks on the real clock, 12 drills of 12 questions for the sections that cost you points, and a predictor that turns your mocks into the odds of reaching your target. One payment, no subscription, and your free score stays free.

Prep courses for these tests usually cost $19 to $129. The CDL Pass Pack is US$39 (£29), once.

See the CDL Pass Pack How our questions are built and checked

8
timed mocks: 12
topic drills: 1
score predictor

Why do so many General Knowledge questions ask about inspection?

Because inspection is a federal duty: you must be satisfied the vehicle is safe before you drive it, and the test checks you know what a defect looks like on every part.

The manual's seven-step inspection is: vehicle overview, check the engine compartment, start the engine and inspect inside the cab, turn off the engine and check the lights, do a walk-around, check the signal lights, then start the engine and check the brakes. Questions ask what you check at a step and what counts as a defect.

The defects worth memorizing: tread under 4/32 inch on a steering tire, a cut or bulge in any tire, mismatched tire sizes, recapped tires on the front of a bus, more than about 10 degrees of steering wheel play (about 2 inches at the rim of a 20-inch wheel), leaking hubs, missing or broken leaf springs, and cracked or loose wheels. If you find one that makes the vehicle unsafe, you do not drive until it is fixed.

What does the test ask about emergencies and skids?

It asks what to do first: steer around a hazard rather than only brake when you cannot stop in time, hold the wheel firmly and stay off the brake in a blowout until you have control, and release the brakes to stop a skid.

Steering to avoid a crash: you can usually steer around an obstacle faster than you can stop. Do not brake while turning, and steer to the right if you must leave the road.
Tire failure: hold the wheel firmly, stay off the brake until the vehicle has slowed, then brake gently and pull off.
Brake failure on a downgrade: use an escape ramp if there is one, and downshift if you can. Do not shift into neutral.
Drive-wheel skid (the most common skid): stop accelerating or braking, let the wheels roll, steer to correct, and counter-steer as needed.
Hydroplaning: release the accelerator and push in the clutch; do not brake.

How should I study for the General Knowledge test?

Read sections 1 to 3 of your state manual once, take the free drill above, then reread only the sections behind your misses; repeat with a full practice test until you clear 80% twice.

The General Knowledge test rewards breadth, so the danger is spending two evenings on shifting and none on cargo. A drill spreads questions across the whole manual and shows where your gaps are. The full CDL practice test adds Air Brakes and Combination, scored separately.

If you will drive a vehicle with air brakes, study the Air Brakes test alongside: stopping distance and brake lag appear on both. For Class A, add the Combination test.

Frequently asked questions

How many questions are on the CDL General Knowledge test?

Washington lists 50 questions with 40 correct needed to pass. Most states use 50; check your own state's page.

Is the General Knowledge test the hardest CDL test?

It is the longest and the broadest. Air Brakes has more numbers per question, but General Knowledge covers far more ground.

Do I need General Knowledge for every class?

Yes. Every CDL applicant takes it, for Class A, B or C.

What section of the manual is General Knowledge?

Usually sections 1 to 3: the introduction, driving safely and transporting cargo safely.

How long should I study?

A week of 45 minutes a day is enough for most people who read the manual once and then practise with explained questions.

Clear 80% with room to spare

Four General Knowledge drills, eight full CDL-style mocks and every answer explained, in one payment.