CDL Permit Test: What to Study and How to Pass

Getting a Commercial Driver’s License (CDL) opens the door to a well-paying career in trucking, bus driving, or other commercial transportation. But before you get behind the wheel of a commercial vehicle, you need to pass the CDL knowledge tests. Here’s everything you need to know to prepare.

CDL Classes: Which One Do You Need?

CDL licenses come in three classes based on the type of vehicle you’ll be driving:

• Class A — Any combination vehicle with a Gross Combination Weight Rating (GCWR) of 26,001+ lbs., where the towed vehicle exceeds 10,000 lbs. (semis, tractor-trailers)
• Class B — Single vehicles over 26,000 lbs. GVWR, or towing a vehicle under 10,001 lbs. (buses, dump trucks, box trucks)
• Class C — Vehicles that don’t meet Class A or B thresholds but carry hazardous materials or 16+ passengers

The CDL Knowledge Tests

Everyone applying for a CDL takes the General Knowledge test. Depending on your vehicle type and endorsements, you may also take additional tests:

• Air Brakes — Required if driving a vehicle equipped with air brakes
• Combination Vehicles — Required for Class A
• Hazardous Materials — Required for HazMat endorsement (also requires a TSA background check)
• Passenger Transport — Required for bus or passenger endorsement
• Tanker — Required for tanker endorsement
• Doubles/Triples — Required for towing double or triple trailers

General Knowledge Test Format

• Questions: 50 multiple-choice questions
• Passing score: 80% (40 correct)
• Topics: Vehicle inspection, basic vehicle controls, shifting, backing, pre-trip inspection procedure, cargo securement, hazard awareness, emergency procedures, and mountain driving

Topics You Cannot Skip

Pre-trip inspection. You must know the proper sequence and what to check at each stage — engine compartment, cab interior, and external inspection. This is heavily tested in the knowledge exam and also required for the CDL skills test.

Cargo securement. Know the rules for securing different types of cargo: minimum number of tie-downs, weight thresholds, edge protection requirements, and which securement methods apply to which cargo types.

Air brakes. If you’re taking the Air Brakes test, know the normal operating pressure range (100–125 psi), low air pressure warning activation point (60 psi), and spring brake activation point (20–45 psi). Also know the brake lag distance and total stopping distance differences between air and hydraulic brakes.

Hours of Service (HOS). Know the 11-hour driving limit, 14-hour on-duty window, mandatory 30-minute break after 8 hours of driving, and the 60/70-hour rule. These numbers come up on the test and matter in real operations.

How to Prepare Effectively

The CDL knowledge tests are based on the Federal Motor Carrier Safety Regulations (FMCSRs) and your state’s CDL manual. Download the New York CDL Manual from the DMV website and work through it chapter by chapter.

Practice tests are especially useful because the real test uses very specific phrasing — and getting comfortable with the wording before test day makes a significant difference in your score. Aim for a consistent 85%+ on practice tests before scheduling your appointment.

After the Written Test

Once you pass all required knowledge tests, you’ll receive your Commercial Learner’s Permit (CLP). You must hold the CLP for at least 14 days before you can take the CDL skills test, which consists of three parts: a pre-trip vehicle inspection, a basic vehicle controls test, and an on-road driving test.

Passing the skills test earns you your full CDL. From there, most employers require a clean driving record and may have additional orientation or training requirements before you start driving commercially.