How CDL knowledge tests are scored

Eighty percent, every test, every state

The figure is federal, so no state can quietly set an easier bar. What states do control is how many questions the test has, and that is where the number people actually care about comes from. Eighty percent of fifty questions means you can get ten wrong. Eighty percent of thirty means you can get six wrong. The percentage never moves; the count of wrong answers you can afford moves with the length of the exam.

Question counts vary by state, and we do not guess at them. Where a state publishes its own count we cite it on that state's page, taken from that state's handbook. Treat any single number you have been told in a yard or a forum as being about the state the person telling you took their test in.

The counts on our practice tests are the shape of our practice run, not a claim about your state's real exam.

Failing air brakes does not stop your license

This is the part that gets misread most often. 49 CFR 383.135(a)(2) says that if an applicant fails the air brake portion of the knowledge test — scores less than 80 percent on it — and is still issued a permit or a license, the state must mark an air brake restriction on it, as required by 49 CFR 383.95(a).

So you can fail air brakes and still walk out with a CDL. It is just a CDL that bars you from driving any commercial vehicle fitted with any type of air brakes. 49 CFR 383.95(a)(2) defines that broadly: air brakes here means any braking system operating fully or partially on the air brake principle. In practice that rules out most of the work the license exists for.

The same restriction lands if you never fail anything. Under 49 CFR 383.135(b)(3), taking your skills test in a vehicle with no air brake system at all produces the same mark.

Because it costs so little to avoid, the air brakes material is worth over-preparing. The air brakes practice test is short, and the questions that catch people are the numbers and the order of the steps, not the concepts.

Combination vehicles works differently

Air brakes gives you a lesser license. Combination vehicles does not.

49 CFR 383.135(a)(3) says a driver applicant who fails the combination vehicle portion of the knowledge test must not be issued a Group A permit or license at all. There is no restricted version. If you want Class A, you pass that test, and the combination vehicles practice test is the one to keep running until coupling, uncoupling and trailer brake questions stop surprising you.

What a restriction actually is

A restriction is a letter on your license that removes something, the mirror image of an endorsement. 49 CFR 383.153 sets the codes: L for no air brake equipped commercial vehicle, Z for no full air brake equipped vehicle, E for no manual transmission, O for no tractor-trailer, M for no Class A passenger vehicle, N for no Class A and B passenger vehicle, K for intrastate only, and V for a medical variance on the driver record.

Most of them come from the vehicle you chose for the skills test rather than from anything you got wrong. 49 CFR 383.95 spells this out. Test in a vehicle with air over hydraulic brakes and you get the full air brake restriction. Test in a vehicle with an automatic transmission and you are restricted from manual transmissions. Test a Group A combination coupled with a pintle hook instead of a fifth wheel and you are restricted from fifth wheel tractor-trailers.

None of that is a punishment. It is the state recording exactly what you demonstrated. But it does mean the truck you borrow for test day decides what your license lets you drive afterwards, which is worth thinking about before you borrow it.

Getting a restriction taken off

You usually do not have to start again. 49 CFR 383.135(b)(7) says an applicant who wants to remove the air brake, full air brake or manual transmission restriction does not have to retake the whole skills test. The state may give a modified skills test showing you can safely operate full air brakes, air over hydraulic brakes or a manual transmission. To take off either air brake restriction you must also perform the air brake pre-trip inspection successfully and pass the air brake knowledge test.

The tractor-trailer restriction is the strict one. Under 49 CFR 383.135(b)(8), removing it means retaking all three skills tests in a representative tractor-trailer.

The skills test is not scored as a percentage

Worth knowing so you do not carry the 80 percent idea across to the wrong exam. 49 CFR 383.135(b)(1) says you must demonstrate all of the skills listed in 49 CFR 383.113 and attain the scores in the examiner manual for the type of vehicle you are testing in.

There is also an automatic failure rule. 49 CFR 383.135(b)(2) says an applicant who does not obey traffic laws, causes an accident during the test, or commits any other offense listed as an automatic failure in the driver and examiner manuals fails the test outright, whatever they scored up to that point.

What a retake involves

Federal rule sets the pass mark. It does not set how soon you may try again, how many attempts you get, or what a retake costs. Those are state decisions, and where a state publishes them we cite them on that state's page rather than repeating a figure that might be a year out of date. Some states make you wait days between attempts. Some let you come back the same week. Assume there is a wait until you have checked your own state's page.

Your scores do not disappear either way. 49 CFR 383.135(c) requires states to record and retain the knowledge and skills test scores of tests taken by applicants, either as part of the driver history record or linked to it.

One practical consequence: if you are close to the line on a section, you are better off waiting and revising than booking again immediately. The mark you need does not move, and the questions you got wrong are the ones you have not learned yet.

Using a practice score honestly

A practice result is only useful if you read it the way the real exam is graded — section by section, not as one average. That is why every run here breaks down by subject rather than handing you a single number. Ninety percent overall with forty percent on air brake material is a fail waiting to happen, and it is a fail you can see coming a week early.

Start where the risk is. Sit the general knowledge practice test first, since every commercial driver takes that exam, then go back over whichever section pulled your score down. The full list of exams is on the CDL practice test hub.