Free CDL study tools
Free CDL Air Brakes Practice Test
Photo by Acroterion · CC BY-SA 4.0. Cropped and resized for this page
What should I study for the CDL air brakes test?
Study brake components, pressure warnings, air lines, parking and emergency functions, trailer protection and license restrictions. If you are preparing a vehicle inspection, learn the manufacturer’s procedure with an instructor; a pressure figure for an older design is not a universal modern test instruction. Use these questions to understand the cited federal requirements and check your state’s testing guidance.
Topics in this set
Brake-system functions, hoses, reservoirs, low-air information, brake condition, ABS and air-brake license restrictions.
50 questions · Practice mode
Last source review: . Source editions and limits are described below.
Practice air brakes
Your result
The knowledge-test pass mark is 80% under 49 CFR 383.135. This independent practice score does not predict an official result.
Your progress and missed-question deck stay in this browser. No account or email is needed.
10 sample questions and answers
Read these examples here, or practice the full set above. The wording is independent study material based on federal sources.
A truck can slow down but cannot hold its combination stationary. Does that meet the general brake requirement?
Answer: No
Required brakes must be adequate to stop and hold the vehicle or combination.
Report a problem with this questionWhich three braking functions have applicable requirements in the general brake rule?
Answer: Service, parking and emergency
The required functions must satisfy the provisions applicable to the vehicle and manufacture date.
Report a problem with this questionFor a modern air-braked truck subject to FMVSS 121, may the applicable manufacture-date standard be ignored?
Answer: No
The in-use rule incorporates the applicable minimum standard for its service and emergency systems.
Report a problem with this questionA required emergency brake control cannot be reached while the driver is belted normally. Is that acceptable?
Answer: No
The applicable emergency control must be operable from the normal restrained driving position.
Report a problem with this questionInterconnected brake systems lose every operative brake when one operating mechanism fails. Is that the intended protection?
Answer: No, the system must preserve operative braking as required
The rule addresses failure protection, with specified scope and exceptions.
Report a problem with this questionAn air-braked combination rolls on a normal dry-road grade under its operating load. Has its parking brake met the holding requirement?
Answer: No
The parking brake must hold under the loading conditions specified by the applicable rule.
Report a problem with this questionDoes a successful parking-brake check with an empty vehicle prove it will hold every permitted load?
Answer: No
The requirement concerns the vehicle or combination under its actual road loading conditions.
Report a problem with this questionFor a vehicle governed by paragraph (c), may a parking brake be held applied solely by air pressure?
Answer: No
That paragraph requires holding energy other than fluid pressure, air pressure or electricity, subject to its stated design provisions.
Report a problem with this questionOn a vehicle governed by paragraph (c), may parking brakes release when insufficient energy remains to reapply them effectively?
Answer: No
The release safeguard is separate from the normal service-brake check.
Report a problem with this questionIs the general rule that a CMV has brakes acting on all wheels?
Answer: Yes, subject to specific exceptions
An exception must actually apply; it is not a reason to ignore a missing required brake.
Report a problem with this question
Sources and study scope
The bank uses original questions based on federal rules and FMCSA material. The questions use the 2025 annual CFR edition, with selected current eCFR references checked on October 28, 2026. It is not a complete review of every later amendment. Each explanation links to its federal source. State manuals are further-study links; no AAMVA manual text is reproduced.
The 80% knowledge-test pass standard comes from 49 CFR 383.135. This site’s practice pool and session lengths do not determine your state’s official test format.