Field Reference Series · CDL & Trucking
CDL Permit Test
Prep Guide
Pass the three tests that earn your commercial learner's permit — General Knowledge, Air Brakes, and Combination Vehicles. Timed practice sets, the PSI numbers you'll actually be tested on, and worked answer keys.
95questions (Class A)
80%to pass each test
3timed practice sets
Try Before You Buy
3 Sample Questions From the Guide
1. The governor cuts the air compressor OUT at approximately:
A. 60 psi B. 90 psi C. 120 psi D. 200 psi
▸ Answer: C. Governor cut-out is around 120 psi (range ~120–140).
2. The low-air warning must come on before pressure drops below:
A. 100 psi B. 80 psi C. 60 psi D. 20 psi
▸ Answer: C. The low-air warning must activate before 60 psi.
3. Off-tracking means the trailer's rear wheels:
A. Follow a wider path than the tractor B. Follow a tighter path in a turn C. Lift off the ground D. Always skid
▸ Answer: B. The trailer's wheels track tighter (inside) the tractor's path — why you swing wide on turns.
What's Inside
How CDL testing actually works (Class A vs B, what's required)
The cheat-sheet numbers to memorize (PSI values, leak limits)
General Knowledge — what's tested + 15-question timed set
Air Brakes — how the system works + 12-question timed set
Combination Vehicles — coupling, off-tracking + 10-question set
Full worked answer keys for every practice set
Endorsements (H/N/T/P/S) & a test-day checklist
Why This Guide
🎯Built around the real test formatThree separate tests, graded individually, all at 80% — studied the way they're actually scored.
🔢The numbers people missGovernor cut-out, low-air warning, spring-brake range, leak limits — the figures that fail people who "studied the concepts."
⏱️Timed practice that mirrors test dayOne set per required test, with worked answer keys so you learn the why, not just the answer.
📱Works anywhereInstant PDF — study on your phone in the yard or at the kitchen table.
Heads up: This is independent study material to help you prep. Test content, question counts, and PSI values vary by state — always study your own state's current official CDL manual, which is the final word.
Independent educational material created by UStradeRoute.com. Not affiliated with, endorsed by, or connected to any state DMV, the FMCSA, AAMVA, or any testing organization. No passing score, permit, or outcome is guaranteed. Operating a commercial vehicle and working around air-brake systems can cause serious injury — never operate equipment you are not trained, licensed, and authorized to operate. © 2026 UStradeRoute.com.