All CDL practice exams
Eight knowledge tests cover every endorsement on a U.S. Commercial Driver’s License. Pick a test below to start practicing.
General Knowledge
The General Knowledge exam is required for every Class A, B, and C CDL applicant. It covers vehicle inspection, basic control, shifting, backing, communicating with other drivers, distracted driving, fatigue, hazard perception, emergency maneuvers, skid control, accident procedures, hazardous materials awareness, and federal hours-of-service rules.
ABAir Brakes
The Air Brakes endorsement covers the operation of compressed-air braking systems used on most heavy commercial vehicles. Topics include compressor and governor operation, supply and service tanks, brake chambers, slack adjusters, dual air systems, parking brakes, low-pressure warning devices, and the seven-step pre-trip air brake test.
CVCombination Vehicles
Combination Vehicles knowledge is required for any driver pulling a trailer with a Class A vehicle. It covers off-tracking, rollover prevention, fifth-wheel coupling and uncoupling, trailer brake operation, antilock braking on trailers, and managing space and stopping distance with a loaded trailer.
HHazardous Materials (H)
The Hazardous Materials endorsement allows a CDL holder to transport materials regulated under 49 CFR. Applicants must pass a TSA threat-assessment background check in addition to a written exam covering hazard classes, the Emergency Response Guide, placarding, shipping papers, segregation rules, loading and unloading, security plans, and route restrictions.
NTanker (N)
The Tanker endorsement is required to haul any liquid or liquefied gaseous material in a permanently mounted cargo tank or portable tank rated for 1,000 gallons or more. Topics include high center of gravity, surge, smooth-bore versus baffled tanks, outage, and emergency procedures for leaks and rollovers.
TDoubles / Triples (T)
Doubles and Triples is required to operate a combination with two or three trailers. The exam covers proper coupling order, converter dolly operation, pintle hooks, weight distribution, off-tracking, and managing the rearward amplification (the "crack-the-whip" effect) when steering.
PPassenger (P)
The Passenger endorsement is required to drive any vehicle designed to carry 16 or more people including the driver. Topics include passenger management, baggage and standee restrictions, prohibited practices, common hazards at stops, railroad crossings, and emergency evacuation procedures.
SSchool Bus (S)
The School Bus endorsement requires Passenger (P) endorsement plus state-specific school-bus knowledge. Topics include the danger zone, mirrors, loading and unloading, post-trip child checks, railroad crossings, emergency exits, and state-mandated student management procedures.
Which tests do I need?
Every CDL applicant takes General Knowledge. From there your test list depends on the vehicle you intend to drive. If your truck has air brakes — and almost all Class 8 trucks do — you also take Air Brakes. If you’ll pull a trailer with a Class A combination, add Combination Vehicles. The remaining five exams (Hazmat, Tanker, Doubles/Triples, Passenger, School Bus) are endorsements you only need if you’ll perform that specific kind of work.
How the tests are scored
All CDL knowledge exams are multiple-choice, with four answer choices per question and one correct answer. The federal passing standard is 80%, and every U.S. jurisdiction follows it. Endorsements range from 20 questions (Tanker, Doubles/Triples, Passenger, School Bus) to 30 questions (Hazmat). The General Knowledge exam itself is approximately 50 questions in most states.
Order of operations
Take the General Knowledge exam first. Air Brakes and Combination Vehicles are commonly taken in the same DMV visit, since most candidates need both. Hazmat requires a TSA background check, so plan to apply for that as soon as you commit to that endorsement — results can take several weeks. Passenger is a prerequisite for School Bus, and School Bus adds state-specific student-management rules on top of the federal Passenger material.