People talk about "the CDL test" as though it were one exam. It is not. The written portion is a set of nine separate tests, and which ones you sit depends on the class of licence you want and the endorsements your job requires.
That is good news, because it means you are almost certainly studying less material than you think. A driver heading for a straight truck job takes a very different set from someone going into tankers.
The first useful thing you can do is work out exactly which tests apply to you. Everything after that gets easier.
The nine tests
The written CDL exams break into three groups.
Core tests — most drivers take these. General Knowledge is required for every CDL, whatever class. Air Brakes applies if the vehicle you will drive has them, which is most commercial trucks. Combination Vehicles applies if you are pulling a trailer, which means anyone going for Class A.
Endorsement tests — only if your job needs them. HAZMAT for hazardous materials. Tanker for liquid bulk. Doubles and Triples for multiple trailers. Passenger and School Bus for carrying people.
The specialised ones. Passenger and School Bus overlap heavily but are separate exams with separate rules.
Which ones do you actually need
Start from the job, not the licence.
If you are driving a tractor-trailer over the road, you are looking at General Knowledge, Air Brakes and Combination Vehicles as your base. Add Doubles and Triples if the fleet runs sets. Add Tanker if there is liquid involved, and note that a tanker endorsement can be required even for a trailer that is only partly full.
If you are driving a straight truck — box truck, dump truck, cement mixer — General Knowledge and Air Brakes usually cover it. Combination Vehicles does not apply unless you pull a trailer.
If you are going into transit or school transport, the Passenger test is your second exam, and School Bus adds a third with its own rules on loading, unloading and student management.
Ask before you study
Call the employer you are aiming at and ask which endorsements they expect on day one. Studying for a test you do not need costs you a week you could have spent on the one you do. It is a two-minute phone call that changes what your whole month looks like.
What the questions are actually like
CDL written questions are multiple choice, drawn from your state's CDL manual, and far more practical than people expect. They are not trick questions. They test whether you know the procedure and the number.
A large share come down to two things: a specific figure — a pressure, a distance, a weight — and a sequence, like the order of steps in an inspection. If you can hold those two categories, you have most of the exam.
The questions people miss are rarely the hardest ones. They are the ones that look obvious and hinge on a detail: which way something is checked, or what the warning device does at a particular threshold.
Building a study routine that survives a work week
The drivers who pass first time are almost never the ones who studied hardest for two days. They are the ones who did twenty questions a day for three weeks.
Spaced repetition is not a study fad here — it is the difference between recognising an answer and recalling it under pressure. Short sessions, repeated, put the material somewhere you can reach it when the screen in front of you is the real one.
A practical rhythm: twenty questions in the morning, review every one you got wrong in the evening. When a topic keeps coming back wrong, read that chapter of the manual rather than grinding more questions on it.
Where the state comes in
One thing to be clear about: the CDL is federal in outline and state in detail. The FMCSA sets the framework, but question counts, passing scores, fees, waiting periods after a failed attempt and even the permit validity window vary from state to state.
Whatever else you use to study, download your own state's CDL manual. It is free from the DMV, and it is the document the questions are written from. Practice tests get you ready; the manual is the authority.
What a practice question cannot do
Practice tests are the fastest way to build recall and to find your gaps. They are not a substitute for the manual, and knowing the difference saves time.
A question can tell you that you do not know the low air warning threshold. It cannot tell you why the threshold exists, and without that, the fact sits in memory unattached to anything and slips out within a week.
The manual supplies the structure — that air brakes are held off by pressure, so every warning is about losing it. Once you have that, the individual numbers hang on something and stay put.
Use questions to find gaps and to rehearse recall. Use the manual to understand what you got wrong. Running only one of the two is the most common inefficiency in CDL preparation.
Studying offline, and why it matters
The places where most people have twenty spare minutes are not the places with reliable signal — a break room, a yard, a waiting area at a terminal.
Study material that needs a connection quietly limits you to the times you are least likely to use it. Offline access is not a feature so much as the difference between a plan you keep and one you abandon.
The same goes for account requirements. A tool that needs a login before it shows you a single question adds a step at exactly the moment when motivation is lowest.
Quick answers
Do I have to take all nine tests?
No. Most drivers take three or four. General Knowledge is universal, Air Brakes applies to most trucks, and Combination Vehicles applies if you pull a trailer. Endorsements are only added if your work requires them.
Are free practice tests good enough to pass?
They are, if the questions are drawn from the same material as the real exam and you use them properly — repeatedly, and with attention to what you get wrong. Practice tests build recall. Reading the manual builds understanding. You want both.
How many questions are on the real test?
It varies by state and by which exam you are taking. General Knowledge is the longest of the core tests in most states. Check your state's DMV page for the exact count and the score you need.
Can I take the tests on different days?
In most states, yes. Many drivers pass General Knowledge first, get the permit, then add endorsements later. Rules on retakes and scheduling differ, so confirm locally before you plan around it.
Where to get it
CDL Prep Exam 2026: Permit covers all nine written tests in one app. It works offline, needs no account, and is free to start — so you can run twenty questions in a break room with no signal.
Work out which tests you need, then practise only those. That focus is worth more than any amount of extra study time.