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Knowledge test: CDL

The knowledge test is available in 4 languages (interpreters aren't allowed):

  • English
  • Spanish
  • Russian
  • Serbian–Croatian

Make an appointment to take the knowledge test at a driver licensing office location that offers testing. The test fee covers 1 attempt at each knowledge test taken within 90 days of the receipt.

You must pass the knowledge test and get a Commercial Learner's Permit (CLP):

  • Before you can take the skills test.
  • Any time you upgrade your CDL by:
    • A higher commercial class
    • Adding endorsements that require a skills test:
      • Passenger endorsement
      • School bus endorsement
      • Tank vehicle endorsement (only if testing and or training in tank vehicle)
    • Removing an air brake restriction

You're required to take the knowledge test any time you:

Knowledge test scores are valid for:

  • 180 days from the date passed.
  • Another 180 days, if you renew your CLP within 30 days of your original CLP expiring. Double, triple, and hazardous materials cannot be renewed with CLP and expire 180 days from the date passed.
CDL knowledge tests
Knowledge test Total questions Passing score Skills test needed
CDL general knowledge (A, B, & C) 50 40 Yes
CDL combination (A) 20 16 Yes
Passenger 20 16 Yes
Air brakes 25 20 Yes
School bus 20 16 Yes
Double/triple 20 16 No
Tank vehicle 20 16 No, unless you're taking your skills test or training in a commercial tank vehicle, then you must take the knowledge test before we can issue your CLP.
Hazardous materials 30 24 No

How to prepare

  • Study the Commercial driver guide to prepare for the test. The guide is only available in English and contains all the information you'll need to pass the test. In the first chapter you will find a table titled "What sections should you study?" This table indicates with an "x" which section(s) you should study before taking the tests.
  • You may also take the practice test for a sample of the types of questions that will be on the test.

Penalties for trying to get a CDL fraudulently could include:

  • Cancellation of your driver license.
  • Having to wait up to 1 year before you can apply again for a CDL.

Questions? Need help?

Call us: 360.902.3900 (TTY: Call 711)

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