Driving · Commercial
CDL Combination Vehicles Test
The knowledge test for a Class A CDL: rollover and skid risks, trailer air brakes, coupling and uncoupling, and combination inspection.
Questions last checked against the official sources on October 10, 2026.
The real exam at a glance
- Questions
- 20 (varies by state)
- To pass
- 80% (16 of 20)
- Time
- About 20 minutes (varies by state)
- Required for
- Class A CDL
- Based on
- Section 6 of your state's CDL manual
What you'll practise
Try a question
What is a bobtail tractor?
- A tractor without a semitrailer
- A tractor pulling two trailers
- A tractor with a sleeper berth
- A tractor with a single drive axle
Show the answer
A. A tractor without a semitrailer — Bobtail tractors are tractors without semitrailers (CDL Manual 6.1.3)
Sample questions by topic (in English)
- Driving combinations safely
- Combination vehicle air brakes
- Antilock brakes on trailers
- Coupling and uncoupling
- Inspecting combinations
- Federal rules
Ask the examiner
Ask about this exam: why an answer is wrong, a grammar point, or “quiz me on …”.
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Questions about the CDL Combination
Is this the official CDL Combination?
No. Semplr is independent and not affiliated with the exam body. We write every question ourselves, in the official format and at the official level.
What is the real CDL Combination like?
Questions: 20 (varies by state). To pass: 80% (16 of 20). Time: About 20 minutes (varies by state). Required for: Class A CDL. Based on: Section 6 of your state's CDL manual.
How is my practice marked?
Instantly. You see your score against the pass mark, and an explanation for every question — including the ones you got right.
Can I take it on my phone?
Yes. The whole mock exam works on a phone, and your progress is saved in your browser.
Ready for a full run?
One sitting, real timing, then your score against the pass mark.
Start the free mock exam