Idaho CDL General Knowledge Test: What to Expect

The Idaho CDL general knowledge test covers commercial-vehicle inspection, safe operation, and cargo fundamentals for all Commercial Driver’s License applicants. The Idaho Transportation Department (ITD), Division of Motor Vehicles, administers the licensing process; the Federal Motor Carrier Safety Administration (FMCSA) requires at least 80% correct on each CDL knowledge examination.

Last verified: November 8, 2026

Start Free Practice Test for Idaho CDL and build your commercial-driving knowledge by topic.

Key takeaways

Idaho commercial applicants need passing knowledge results before moving through the permit and skills stages described by ITD’s CDL steps and the FMCSA testing standard.

• Idaho CDL knowledge examinations require at least 80% correct under the FMCSA standard.
• Idaho charges $5 for each CDL knowledge test, according to ITD.
• Idaho requires a 3-day wait after a failed CDL knowledge examination before retesting, with another $5 testing fee.
• Idaho knowledge-test passes remain valid for 1 year, according to ITD’s licensing steps.

Which knowledge exams belong on your Idaho application?

The Idaho CDL Manual requires General Knowledge for every commercial applicant and additional examinations according to vehicle equipment, combination configuration, and intended cargo or passengers.

Read the testing section of the ITD CDL Manual before selecting exams. Class A combination drivers need combination-vehicle knowledge. A Class B straight-truck applicant does not automatically need every endorsement examination. Class C commercial operations can involve passenger or hazardous-material requirements rather than the same study package as a tractor-trailer.

• General Knowledge: the common foundation for CDL applicants, including inspection, safe driving, emergencies, and cargo.
• Air Brakes: needed for operating applicable air-brake-equipped vehicles, including air-over-hydraulic systems. Air-brake restrictions concern equipment qualifications; “air brakes” is not the name of an endorsement.
• Combination Vehicles: the knowledge needed for combination operation, including coupling and trailer behavior.
• Passenger and School Bus: additional knowledge for the respective bus operations, with applicable skills and training requirements.
• Hazardous Materials, Tank Vehicles, and Doubles/Triples: specialized subjects tied to the loads or configurations you intend to operate.

For a first Class A or Class B license, an applicable Class B-to-A upgrade, or a first Passenger, School Bus, or Hazardous Materials endorsement, review the manual’s Entry-Level Driver Training requirements. Hazardous Materials also involves Transportation Security Administration screening. Passing General Knowledge alone does not complete those processes.

How should you divide commercial knowledge study?

Idaho commercial preparation should begin with the CDL Manual’s general driving and cargo sections, then add the equipment and endorsement sections for the intended vehicle.

Start with inspection logic: identify the component, recognize an unsafe condition, and understand what failure would do. Continue with shifting, stopping, space management, curves, night driving, weather, and emergencies. Study cargo securement and weight distribution as driving-safety subjects, rather than treating them as paperwork.

Build scenarios around the vehicle you expect to operate. An unloaded straight truck, a loaded combination, and a passenger bus do not respond identically. Ask which feature changes the stopping or turning decision. Then read the appropriate specialized section instead of transferring every ordinary-car habit to a commercial vehicle.

Our Idaho CDL practice collection offers 20 tests and 224 unique questions. Practice tests contain 50 questions with a 40-correct practice target. Review missed topics against the manual before starting a different set; do not substitute a remembered answer order for understanding vehicle behavior.

What does a hydraulic-brake question test?

An Idaho commercial driver facing loss of hydraulic pressure can use a lower gear to help slow the vehicle, according to the CDL Manual’s brake-failure section.

After answering, explain why upshifting would not provide the needed slowing effect. That comparison reveals whether you understand the vehicle response or merely recognized a familiar phrase.

What happens between knowledge testing and the skills exam?

Idaho’s Commercial Learner’s Permit costs $29, lasts 1 year, and must be held for at least 14 days before the CDL skills test, according to ITD’s commercial licensing steps.

Complete the applicable application, medical-certification, training, and supervision requirements for your operation. The knowledge stage prepares you to begin the permitted learning process; the later skills examination assesses inspection, vehicle control, and road driving in an appropriate commercial vehicle.

If an Idaho knowledge attempt fails, ITD requires a 3-day wait and another $5 fee for that examination. Passed knowledge results remain valid for 1 year; after that period, the ITD steps require written examinations again if the CDL has not been issued.

Use the Idaho CDL hub for the commercial route. Applicants still working toward an ordinary license can review Idaho Class D licensing and the car permit study plan; the car road-test checklist addresses a different examination.

Start Free Practice Test for Idaho CDL and concentrate on the commercial topics behind your missed answers.

Frequently asked questions

Idaho CDL applicants should match preparation to their commercial vehicle rather than apply the ordinary Class D test format to commercial licensing.

Does a car permit-test pass replace General Knowledge?

Idaho’s ordinary Class D knowledge examination does not replace the commercial General Knowledge requirement. The commercial manual adds vehicle inspection, cargo, and heavy-vehicle operating subjects.

Can I add every endorsement by passing written questions?

Idaho endorsements can require training, screening, or skills testing in addition to knowledge examinations. Passenger and School Bus qualifications, for example, involve more than selecting correct answers on a computer.

Should I learn the air-brake section for a hydraulic-only vehicle?

The Idaho manual ties the Air Brakes examination to operating an applicable air-brake-equipped vehicle. Discuss the planned test vehicle and resulting restrictions with the licensing office so your study and skills-test arrangements match your intended work.