General Knowledge
License classes, endorsements and why inspections matter.
1.1 CDL classes
A commercial driver's license (CDL) is issued in three classes. The class depends on the weight ratings of the vehicle you drive and on what you carry.
| Class | What it covers |
|---|---|
| A | Any combination with a gross combination weight rating (GCWR) of 26,001 lb or more, when the towed vehicle(s) are rated over 10,000 lb |
| B | A single vehicle rated 26,001 lb or more, or such a vehicle towing a vehicle rated 10,000 lb or less |
| C | A vehicle that is not Class A or B but is designed to carry 16 or more passengers (including the driver) or is used to transport placarded hazardous materials |
Eslatma: Ratings (GVWR/GCWR) are set by the manufacturer — not the actual weight on the scale today.
Tekshiruv A tractor rated 30,000 lb pulls a trailer rated 20,000 lb. Which class is required?
Manba: FMCSA — 49 CFR Part 383 — Commercial Driver's License Standards (eCFR current), 49 CFR 383.91. Yangilangan: 2026-10-09
1.2 Endorsements and restrictions
Some vehicles and loads require an extra knowledge test (and sometimes a skills test).
- H — Hazardous materials (also requires a TSA security threat assessment)
- N — Tank vehicle
- P — Passenger
- S — School bus
- T — Double/triple trailers
- X — Combination of tank vehicle and hazardous materials
Restrictions are added when you test in a vehicle that lacks certain equipment, for example when the skills test is taken in a vehicle without full air brakes or with an automatic transmission.
Maslahat: Check your state's CDL manual for the exact restriction codes your state prints on the license.
Manba: FMCSA — 49 CFR Part 383 — Commercial Driver's License Standards (eCFR current), 49 CFR 383.93, 383.95. Yangilangan: 2026-10-09
1.3 Why vehicle inspections matter
Safety is the main reason to inspect your vehicle. A defect found in the yard costs minutes; a defect found on the highway can cost lives.
- Pre-trip: before driving, to find problems that could cause a crash or breakdown.
- During the trip: watch gauges, use your senses (look, listen, smell, feel) and check tires, brakes, lights, coupling and cargo at every stop.
- Post-trip: at the end of the day; report defects on a driver vehicle inspection report (DVIR) when required.
Diqqat: Federal and state inspectors can place an unsafe vehicle "out of service" until it is repaired.
Manba: FMCSA — 49 CFR Part 396 — Inspection, Repair, and Maintenance (eCFR current), 49 CFR 396.11, 396.13. Yangilangan: 2026-10-09