The Colorado CDL knowledge exam is not one test — it is a series of separate tests depending on which CDL class and endorsements you are seeking. Each test has a different number of questions, a different passing threshold, and covers different content from the official Colorado CDL Driver Manual (Form DR 2251). This guide gives you the exact question count, passing score, and topic breakdown for every Colorado CDL knowledge test in 2026.
| Test | Questions | Pass Score | Min. Correct | Required For |
|---|---|---|---|---|
| General Knowledge | 50 | 80% | 40 | All CDL applicants |
| Air Brakes | 25 | 80% | 20 | Vehicles with air brakes (remove restriction) |
| Combination Vehicles | 20 | 80% | 16 | Class A CDL (tractor-trailers) |
| Hazardous Materials (H) | 30 | 80% | 24 | Hazmat endorsement |
| Tanker (N) | 20 | 80% | 16 | Tanker endorsement |
| Doubles and Triples (T) | 20 | 80% | 16 | Doubles/Triples endorsement |
| Passenger (P) | 20 | 80% | 16 | Passenger endorsement |
| School Bus (S) | 25 | 80% | 20 | School Bus endorsement |
Blue left border = required test. Amber left border = optional endorsement test.
For a Colorado Class A CDL with air brakes: You must pass General Knowledge (50 questions), Air Brakes (25 questions), and Combination Vehicles (20 questions) — a total of 95 knowledge test questions across three separate tests, all at the same DMV appointment.
The General Knowledge test is the foundation of the Colorado CDL knowledge exam. Every CDL applicant takes this test regardless of license class or endorsements sought. It is based on Sections 1 through 4 of the Colorado CDL Driver Manual (DR 2251).
The Air Brakes test is required if the vehicle you are seeking a CDL for has air brakes. If you skip this test or fail it, your CDL will have an air brake restriction — meaning you cannot legally drive any vehicle equipped with air brakes. Most Class A commercial trucks use air brakes, so skipping this test severely limits your career options. It is based on Section 5 of the Colorado CDL Driver Manual.
FastLessonHub tip: The Air Brakes test has the most specific number memorization of any CDL test. Know these numbers cold: normal air pressure (100–125 PSI), low pressure warning (60 PSI), spring brake application (20–45 PSI), and the 3-step LAB check sequence. Our free Air Brakes practice test covers all 140 questions mapped to Section 5 of the DR 2251.
The Combination Vehicles test is required for Class A CDL applicants — anyone seeking to drive tractor-trailers, tanker combinations, or other combination vehicles. It is based on Section 6 of the Colorado CDL Driver Manual.
Endorsements allow you to operate specialized vehicles or haul specific types of freight. Each endorsement requires passing an additional knowledge test at the Colorado DMV. Some endorsements also require ELDT theory training before you can take the knowledge test.
Hazmat test language restriction: The Colorado CDL Hazmat knowledge test is available in English only. All other CDL knowledge tests in Colorado are available in both English and Spanish. If English is not your primary language, be aware of this limitation before scheduling your Hazmat test.
All Colorado CDL knowledge tests are administered on a computer at the DMV. Questions are multiple choice with four answer choices (A, B, C, D). You can navigate between questions and change answers before submitting. The computer displays your score immediately after you finish.
If you are applying for a Class A CDL with air brakes, you can take all three required tests — General Knowledge, Air Brakes, and Combination Vehicles — in a single DMV appointment. Plan for 2 to 3 hours for your appointment when taking multiple tests. Tests are taken one at a time on the computer.
Every Colorado CDL knowledge test requires a minimum 80% score. There is no rounding up. If the passing threshold is 40 out of 50, you need exactly 40 — 39 is a failing score. Aim for 85%+ in practice before your appointment to give yourself a comfortable buffer for test-day nerves.
Your knowledge test results are only valid for one issuance of a Commercial Learner's Permit. Once your CLP is issued, if you decide to change your CLP class or add endorsements, you must retake all required exams. Choose the class and endorsements you want before taking your knowledge tests.
Important: The Colorado DMV strongly recommends taking all required knowledge tests at the same appointment. Taking them on separate days means multiple DMV appointment wait times and may create complications if you want to change your CLP class or endorsements later.
There is no limit on the number of retake attempts for Colorado CDL knowledge tests. You can retake each test as many times as needed until you pass.
Colorado requires a minimum 1-day waiting period between CDL knowledge test attempts. You cannot retake a failed test the same day. Each retake requires a new DMV appointment.
If you fail one test during your appointment but pass others, you only need to retake the test you failed. You do not need to retake the tests you already passed. Your passing test results are saved in the system.
The CDL skills test (pre-trip, backing, road test) is different from the knowledge tests and is taken at a third-party testing facility. If you fail any component of the skills test, you must retake only the failed component — not the entire test. Each retake costs approximately $275. There is no limit on skills test retakes, and Colorado does not impose a waiting period between skills test attempts beyond scheduling availability.
All Colorado CDL knowledge test questions come directly from the official Colorado CDL Driver Manual (Form DR 2251), published by the Colorado Division of Motor Vehicles. You can download it free at dmv.colorado.gov.
Use our free practice tests. Our Colorado CDL practice tests are mapped directly to the DR 2251 manual and include all three required knowledge areas — General Knowledge, Air Brakes, and Combination Vehicles. Each question includes a rationale explaining why the correct answer is right. No signup required.
The answer depends on which tests you are taking. For a Class A CDL with air brakes — the most common path — you take three tests totaling 95 questions: General Knowledge (50 questions), Air Brakes (25 questions), and Combination Vehicles (20 questions). Each test must be passed separately with a score of 80% or higher.
The passing score for all Colorado CDL knowledge tests is 80%. You must correctly answer at least 80% of the questions on each individual test. There is no combining scores across tests — each test must independently reach 80%.
Each test takes approximately 20 to 45 minutes depending on how quickly you work through the questions. If you are taking all three tests for a Class A CDL with air brakes, plan for 1 to 2 hours of testing time plus DMV check-in and processing time. Your total DMV appointment may run 2 to 3 hours.
Yes. All Colorado CDL knowledge tests are available in both English and Spanish — except the Hazmat endorsement test, which is available in English only. When booking your DMV appointment, notify the office if you need the Spanish version.
If you fail one test but pass others at your DMV appointment, you only need to retake the failed test. You do not lose credit for tests you passed. There is no limit on retakes and Colorado requires a 1-day minimum waiting period between attempts. Each retake requires a new DMV appointment.
Technically no — but practically yes. The Air Brakes test is not legally required to receive a Class A CDL. However if you do not take it and pass, your CDL will have an air brake restriction that prohibits you from operating any vehicle with air brakes. Since virtually all tractor-trailers use air brakes, an air brake restriction makes your Class A CDL nearly useless for commercial trucking. Take the Air Brakes test.
Our free practice tests cover General Knowledge, Air Brakes, and Combination Vehicles — all 560 questions mapped to the official Colorado CDL Manual. No signup required.
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