CDL General Knowledge Test: What to Expect & How to Pass

The CDL General Knowledge test is the first written exam every commercial driver must pass, regardless of the class of CDL you're pursuing. It's the foundation for your commercial driving career. Here's everything you need to know to pass it.

Test Overview

• Number of questions: 50 (varies slightly by state)
• Passing score: 80% (40 out of 50 correct)
• Time limit: Usually 60-90 minutes
• Format: Multiple choice
• Required for: All CDL classes (A, B, and C)

Topics Covered

Vehicle Inspection

You'll need to know how to perform a proper pre-trip inspection, what to check, and why each component matters. This includes tires, brakes, lights, mirrors, coupling devices, and fluid levels.

Basic Vehicle Control

Questions cover steering, backing, shifting, and managing speed on grades. Understanding the relationship between vehicle weight, speed, and stopping distance is critical.

Safe Driving

This is the largest section. Topics include:

• Space management and following distance
• Speed management on curves, hills, and in bad weather
• Night driving techniques
• Sharing the road with smaller vehicles
• Distracted and drowsy driving

Transporting Cargo

Proper cargo securement, weight distribution, and load balance. You'll need to understand how improperly loaded cargo affects vehicle handling and braking.

Hours of Service (HOS)

Federal regulations on driving hours, required breaks, and logbook requirements. Key numbers to memorize:

• 11-hour driving limit
• 14-hour on-duty window
• 60/70-hour weekly limits
• 30-minute break requirement
• 10-hour off-duty requirement

Accident Procedures

What to do at the scene of an accident, reporting requirements, and how to protect the scene.

Study Strategies

1. Read the CDL manual — Your state's CDL manual covers everything on the test
2. Take practice tests repeatedly — Aim for consistently scoring 90%+ before scheduling your test
3. Focus on weak areas — Track which categories you miss most and drill those
4. Learn the "why" — Understanding the reasoning behind rules helps you answer questions even when they're worded differently
5. Study in short sessions — 20-30 minutes at a time, multiple times per day

Common Mistakes to Avoid

• Confusing stopping distance formulas at different speeds
• Mixing up HOS rules (11-hour vs 14-hour vs 60/70-hour)
• Not knowing the difference between controlled and uncontrolled railroad crossings
• Forgetting tire tread depth requirements (4/32" for steering, 2/32" for others)
• Rushing through questions — read each one carefully