CDL · 20% of test plan

General Knowledge for the CDL Exam

Every CDL applicant takes General Knowledge. Topics include vehicle inspection, basic control, shifting, communicating with other drivers, accident procedures, and driver wellness.

Locale-specific study guides

Pass-rate data, regulatory context, and study tips for General Knowledge all change by candidate locale. Pick your context:

Common failure modes

These are the patterns that cause most candidates to lose marks on this topic. Recognising them in advance is half the work.

!Misidentifying the controlled-braking vs stab-braking technique
!Confusing the proper following distance rule (1 second per 10 ft of vehicle length, plus 1 second above 40 mph)
!Wrong answer on hazardous-conditions reduced-speed rules
!Confusing the disqualification offences (DUI, reckless, leaving the scene)

Study tips

1Drill following-distance math: 50 ft trailer at 35 mph = 5 seconds; at 50 mph = 6 seconds.
2Memorize disqualification offences and their durations — first DUI = 1 year, second = lifetime.
3Practice stab-braking vs controlled braking with the FMCSA definition.
4Know the wellness requirement: 8 hours sleep, no driving over 11 hours after 10 off.

Sample CDL General Knowledge questions

These sample items mirror the format and difficulty of real CDL questions. Practice with thousands more on the free Koydo question bank.

1
You should keep how many seconds of following distance for every 10 feet of vehicle length at speeds below 40 mph?
- A1 secondCorrect
- B2 seconds
- C3 seconds
- D5 seconds
Why this answer?
The CDL rule is 1 second per 10 feet of vehicle length below 40 mph. Above 40 mph, add 1 second. A 60-foot rig at 55 mph thus needs 7 seconds of following distance.

Practice CDL questions free with Koydo.

Air-brakes, hazmat, pre-trip — every endorsement, every state. Built with a Pass Guarantee.

Start free CDL practice →See CDL pass rates by state