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CDL · General Knowledge · California, USA

General Knowledge for the CDL Exam — California candidates

20% of the CDL test plan. The General Knowledge test (50 multiple-choice questions) is required for every CDL class and covers vehicle systems, road rules, and emergency procedures. Calibrated for Californian candidates.

High-stakes exams reward two skills equally: knowledge and test-craft. This page focuses on both for one of the most failure-prone areas. General Knowledge sits at roughly 20% of the Commercial Driver License content distribution — Every CDL applicant takes General Knowledge. Topics include vehicle inspection, basic control, shifting, communicating with other drivers, accident procedures, and driver wellness. Pass rates for the CDL are published annually by the awarding body and vary by cohort and locale. For California candidates preparing for CDL, the calibration of study to local context matters: California is the largest U.S. testing market for NCLEX, MCAT, SAT, and ACT. The CA Board of Registered Nursing has notoriously long endorsement timelines (8–14 weeks).

Pass rates for CDL (California, USA) are published periodically by the awarding body.

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.
  • 5For NCLEX-RN: the California Board of Registered Nursing requires LiveScan fingerprinting before ATT release; book early because LiveScan vendors fill 2–3 weeks out.
  • 6For MCAT/SAT/ACT: California universities are test-blind for SAT/ACT undergraduate admission as of 2024; verify whether your target medical/grad programs still require MCAT/GRE.
  • 7For CDL: California has its own "California Special Requirements" addendum on top of FMCSA; review the CA Commercial Driver Handbook before sitting the written test.

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. 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.

Frequently asked questions

How many questions are on the General Knowledge test?
Most states use a 50-question multiple-choice format. You must answer at least 40 (80%) correctly to pass.
What is the CDL pass rate for Californian candidates?
Pass rates for CDL candidates in California, USA are published periodically by the awarding body. Practice questions, full-length simulations, and weak-area drills are the highest-impact way to improve your odds.
How long should Californian candidates study General Knowledge for the CDL?
For most candidates, focused mastery of General Knowledge requires 20–40 hours of deliberate practice — drilling sample questions, reviewing failure modes, and timing yourself against exam conditions. California is the largest U.S. testing market for NCLEX, MCAT, SAT, and ACT. The CA Board of Registered Nursing has notoriously long endorsement timelines (8–14 weeks). Combine General Knowledge study with full-length mock exams in the final two weeks before your test date.

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