CDL Endorsements Bundle Pass Rate, Format & Study Guide

Air Brakes, Combination Vehicles, and the Tanker endorsement are three separate written knowledge tests administered by state DMVs/DPSs as part of the Class A Commercial Driver's License (CDL) permit process, under federal minimum standards set by the Federal Motor Carrier Safety Administration (FMCSA) in 49 CFR Part 383. Unlike a standalone professional certification issued by one national body, there's no single 'CDL Endorsements' credential — each of these is a distinct pass/fail knowledge test tied directly to what a driver is legally permitted to operate: air-brake-equipped vehicles, combination (tractor-trailer) vehicles, and tank vehicles hauling liquid or gaseous cargo, respectively. This portal bundles all three because most Class A applicants need Air Brakes and Combination Vehicles together by default, with Tanker as a common third addition for drivers pursuing tank-hauling work.

Nearly every real-world Class A driving job requires operating a combination vehicle with air brakes, which is why Air Brakes and Combination Vehicles function as practical requirements for almost any Class A career, not optional add-ons. The Tanker endorsement specifically opens up a distinct, often better-compensated segment of trucking work — fuel, chemical, food-grade liquid, and other tank-hauling routes — that a standard dry-van Class A license doesn't qualify a driver for. Because a missing endorsement or restriction (an 'L' restriction on the license itself marks a driver as barred from operating air-brake vehicles) can disqualify a driver from an otherwise-available job on the spot, passing these knowledge tests before actively job-hunting removes a real, avoidable bottleneck between licensure and employment.

Anyone pursuing a Class A CDL for the first time, since Air Brakes and Combination Vehicles cover the vehicle types the large majority of Class A jobs actually use. Existing CDL holders who currently carry an 'L' (air brake) restriction and want to remove it to open up more job opportunities are also a direct fit for the Air Brakes section specifically. Drivers specifically targeting tank-hauling routes (fuel delivery, chemical transport, food-grade liquid hauling) are the target audience for the Tanker section, on top of whichever of the other two sections they still need.

The certifying body does not publicly publish an official pass rate for this exam. Be wary of third-party sites citing a specific number here — treat any pass-rate claim you see elsewhere for this exam as unverified.

No single national retake policy — 49 CFR 383.135 sets the federal-minimum 80% passing bar for every CDL knowledge test, but wait periods and any retake fees for Air Brakes, Combination Vehicles, and Tanker are each set at the state DMV/DPS level, so they vary by state. Each section is scored independently — failing one doesn't require retaking a section you already passed.

Each of the three sections is pass/fail against the same federal-minimum 80% correct threshold (49 CFR 383.135): Air Brakes is scored out of 25 questions (20 correct to pass), Combination Vehicles out of 20 (16 correct), and Tanker out of 20 (16 correct). Most states administer these as computer-based tests drawn from a standardized question bank aligned to each state's own CDL manual.

Each section is administered as its own separate, state-run computer-based knowledge test at the same DMV/DPS office (or approved third-party testing site) where the CDL permit's General Knowledge test is taken — most states allow a candidate to sit for several sections in the same visit. Air Brakes is 25 questions, Combination Vehicles is 20 questions, and Tanker is 20 questions; all three use multiple-choice format drawn from each state's own CDL manual, which is itself based on a common federally-influenced content standard (many states draw from the AAMVA-model question bank) even though the exact question pool differs state to state.

Air Brakes covers the mechanical fundamentals of air brake systems (compressor, reservoirs, brake chambers, slack adjusters), the required pre-trip inspection steps specific to air brakes, dual air brake systems, and how to recognize and respond to air brake system problems on the road — this is the section a driver must pass to remove the 'L' restriction and legally operate any air-brake-equipped vehicle. Combination Vehicles covers coupling and uncoupling a tractor-trailer, how combination vehicles handle differently from a straight truck (stopping distance, off-tracking on turns, splitting/managing weight), and inspecting the connections between tractor and trailer. Tanker covers the specific hazards of hauling a partially-loaded liquid tank (surge, the effect of liquid movement on vehicle handling and stopping), safe driving practices for curves and turns with a high center of gravity, and inspecting/maintaining a tank vehicle's specific equipment (baffles, vents, emergency shutoff devices where applicable).

There's no eligibility gate specific to these three knowledge tests beyond already holding, or actively applying for, a Class A CDL permit at your state DMV/DPS — no separate experience or education requirement, no minimum hours behind the wheel, and no federal age requirement beyond whatever your state already requires for the underlying CDL permit (commonly 18 for intrastate driving, 21 for interstate). A driver who already holds a CDL without one of these endorsements can typically add it later by passing just that section's knowledge test (and, for some endorsements in some states, a skills component) without reapplying for the permit itself.

There is no federal fee for any of these three sections — FMCSA sets the content and passing standard (49 CFR Part 383), but each state DMV/DPS sets its own testing fee structure, and many states bundle knowledge-test fees into the overall CDL permit application fee rather than charging per section. Budget for your specific state's published CDL fee schedule, and check whether retesting a failed section carries its own separate fee (state-dependent, not federally standardized).

These are one-time knowledge tests tied to what's printed on your CDL, not a recertifying credential with an ongoing CE requirement — once a section is passed and the corresponding endorsement or removed restriction is reflected on your CDL, there's no periodic retest requirement to keep it, beyond your state's normal CDL renewal cycle (which does not require retaking these knowledge tests in most states, only a vision/medical recheck and the standard renewal process).

These are three separate, relatively short knowledge tests rather than one long exam, so most candidates study each section directly from their state's CDL manual chapter by chapter — Air Brakes and Combination Vehicles together first (since nearly every Class A applicant needs both), then Tanker only if that endorsement is actually needed. A few days to a week of focused manual review per section is typical, longer for candidates without prior air-brake or combination-vehicle driving experience to draw on.

No structural changes to the federal 80% passing standard (49 CFR 383.135) or the general knowledge-test framework for these three sections have been publicly announced as of August 2026. Because each state administers its own specific test bank and fee schedule under this shared federal floor, always check your own state DMV/DPS's current CDL manual and fee schedule directly rather than assuming another state's specifics apply.