CDL General Knowledge Cheat Sheet (2026)
CDL exam basics
| Item | Detail |
|---|---|
| General knowledge questions | 50 questions |
| Passing score | 80% — 40 of 50 correct |
| Air brakes (if applicable) | 25 questions, 80% to pass |
| CDL classes | Class A (combo >26,001 lb), B (single >26,001 lb), C (hazmat/16+ passengers) |
Pre-trip inspection — 7 steps
| Step | What to check |
|---|---|
| 1. Engine compartment | Oil, coolant, power steering, battery, belts, hoses, leaks |
| 2. Cab / in-cab | Mirrors, horn, wipers, gauges, seatbelt, emergency equipment |
| 3. Lights | Headlights, turn signals, brake lights, marker lights, clearance lights |
| 4. Fuel / leaks | Fuel tank, lines, no dripping under vehicle |
| 5. Tires | Tread depth ≥ 4/32″ (steer), ≥ 2/32″ (other); inflation; no bulges |
| 6. Brakes | Brake drums, slack adjusters, brake lines, air hose connections |
| 7. Coupling (combo vehicles) | Fifth wheel, kingpin, landing gear, trailer connections |
Hours of service — key limits
| Rule | Limit |
|---|---|
| Driving window | Must drive within 14-hour on-duty window |
| Max driving time | 11 hours after 10 consecutive hours off |
| 30-minute break | Required after 8 cumulative hours driving |
| Weekly limit (7-day) | 60 hours on duty in 7 days |
| Weekly limit (8-day) | 70 hours on duty in 8 days |
| 34-hour restart | Resets weekly clock after 34 consecutive off-duty hours |
Air brakes — critical numbers
| Test / reading | Standard |
|---|---|
| Normal operating pressure | 100–125 psi |
| Low air warning activates | 60 psi or below |
| Spring brakes apply (tractor) | 20–45 psi |
| Static leakage test (single) | ≤ 3 psi drop in 1 minute |
| Static leakage test (combination) | ≤ 4 psi drop in 1 minute |
| Governor cut-out | ~125 psi |
| Governor cut-in | ~100 psi |
Cargo securement — key rules
Working Load Limit (WLL) of all tie-downs combined must equal at least half the cargo weight. Inspect cargo within first 50 miles, then every 3 hours or 150 miles.
Stopping distance (at 55 mph, dry road)
| Vehicle | Approximate stopping distance |
|---|---|
| Passenger car | ~133 feet |
| Loaded truck | ~196 feet |
| Empty truck | ~More than loaded (less traction) |