Oregon Air Brakes Practice Test

Required if the vehicle you'll drive has air brakes — which in practice means nearly every combination vehicle and most straight trucks. The test covers the parts of an air-brake system (compressor, governor, tanks, valves), the specific pressures where things happen (cut-in, cut-out, low-air warning, spring-brake pop-out), and the inspection sequence for leaks and warning devices. Fail this knowledge test or take the skills test in a vehicle without air brakes, and your license carries an air-brake restriction that keeps you out of most trucking jobs.

Who needs it: Anyone who'll drive a vehicle with air brakes. Skipping it puts an L or Z restriction on the license.

Sample practice questions

"Fanning" the brakes (pressing and releasing repeatedly) is dangerous because it:

Answer: Can release air faster than the compressor can replace it — Unnecessary fanning can drop pressure too low to brake because air leaves faster than it's replaced.

The alcohol evaporator helps:

Answer: Reduce the risk of ice in air brake valves in cold weather — Alcohol reduces ice formation in the valves; you must still drain tanks daily.

Using the proper braking technique, after braking you release the brakes when your speed is about:

Answer: 5 mph below your safe speed — Brake to feel a slowdown, then release at about 5 mph below your safe speed (a roughly 3-second application), and repeat.

Common mistakes on the Air Brakes test

  • Mixing up the pressure numbers — cut-out (~125 psi), cut-in (~100 psi), low-air warning (~60 psi) are all tested
  • Confusing spring brakes (parking/emergency) with service brakes — which system does what, and when
  • Forgetting the air-leak rate limits for the applied and released tests during inspection
  • Assuming ABS changes how you brake — the test wants normal braking with ABS, not pumping

Studying with the full Truckcess course does double duty: the theory counts toward the federal ELDT requirement (Truckcess is listed on the FMCSA Training Provider Registry).

Official source: Oregon Driver & Motor Vehicle Services (ODOT)

CDL licensing in Oregon is administered by the Oregon Driver & Motor Vehicle Services (ODOT). Fees, scheduling, forms, and the official Oregon CDL manual live on the official site: Oregon DMV — official CDL page (verified 2026-08-09).

Truckcess is not affiliated with or endorsed by the Oregon Driver & Motor Vehicle Services (ODOT). Our practice tests cover the federal CDL knowledge standards (49 CFR Part 383) that every state exam is built on; exact question counts, fees, and procedures vary by state and change over time — the official site is always the authority.

More Oregon practice tests

Full prep courses are one-time from $59 with 12 months of access — mytruckcess.com/cdl.

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