Idaho CDL General Knowledge Test (ID) 5

4.9 out of 5 (45 votes)
80% Passing score
50 Questions
10 Mistakes allowed
In the realm of commercial driving, a solid foundation of knowledge is not just a requirement but a necessity for safety and success. That's where our Idaho CDL General Knowledge Practice Test comes into play. As the fifth in our series of practice tests, it is designed to be a comprehensive tool for those preparing to earn their commercial driver's license (CDL) in Idaho in 2026. Our practice test features 50 carefully crafted Idaho CDL general knowledge questions that mirror the style and scope of the actual CDL exam. To pass, you'll need to correctly answer at least 40 of these questions. The beauty of our practice test lies in its consistency; the same set of Idaho CDL questions and answers is presented each time you attempt the test, allowing you to measure your progress and identify areas where further study is needed. Staying abreast of the latest regulations and laws is crucial for every commercial driver. Understanding this, our Idaho CDL practice test is regularly updated to reflect the most current driving laws and regulations as of 2026. This ensures that you are studying the most relevant and up-to-date information, giving you an edge in your test preparation. Moreover, our CDL general knowledge practice test isn't just a generic tool; it's tailored specifically for Idaho. This means that you'll encounter questions that are relevant to the unique driving conditions, laws, and road signs found in Idaho, giving you a more realistic and state-specific preparation experience. Whether you're a seasoned driver brushing up your knowledge or a newcomer stepping into the world of commercial driving in 2026, our Idaho CDL General Knowledge Practice Test is a dependable resource. It's more than just a test; it's your pathway to mastering the essentials of commercial driving in Idaho.
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Sample Idaho CDL Test Questions - General Knowledge

Question 1

At highway speed, how far ahead represents a 12- to 15-second visual lead?

  1. A About one-eighth mile
  2. B About one-quarter mile
  3. C About one-half mile
  4. D About three-quarters mile

Correct answer: B – About one-quarter mile

A commercial driver should generally look at least 12 to 15 seconds ahead while continuing to monitor nearby traffic. At highway speeds, that visual lead is approximately one-quarter mile. Looking well ahead provides more time and distance to respond gradually when traffic slows, lanes close, or another hazard develops.

Source: Idaho Commercial Driver’s License Manual — § 2.4.1, “Seeing Ahead”

Question 2

What does a yellow diamond sign showing another lane joining your roadway warn you about?

This sign warns drivers to _____________.
  1. A Emergency vehicles regularly cross at that location
  2. B Traffic may merge into your roadway ahead
  3. C All vehicles must stop before the junction
  4. D The road changes to two-way traffic

Correct answer: B – Traffic may merge into your roadway ahead

A Merge sign warns that vehicles from separate roadways may converge into a single traffic lane. Drivers should watch the entering traffic and adjust safely for the developing conditions. The sign used on Idaho highways is a warning of the merge; it is not a stop sign and does not by itself assign a new right-of-way rule.

Source: Manual on Uniform Traffic Control Devices for Streets and Highways, 11th ed., Revision 1 — § 2C.45, “Merge Signs and Plaque (W4-1, W4-5, and W4-5aP)”

Question 3

Which serious hazard can result when wet brakes apply unevenly or grab?

  1. A Automatic transmission failure
  2. B Loss of engine lubrication
  3. C Headlight failure
  4. D A trailer jackknife

Correct answer: D – A trailer jackknife

Water can make brakes weak, uneven, or prone to grabbing. Possible results include reduced braking power, locked wheels, pulling to one side, and a jackknife when pulling a trailer. After passing through unavoidable deep water, follow the manual's procedure for applying light brake pressure, drying the brakes, and testing them when it is safe.

Source: Idaho Commercial Driver’s License Manual — § 2.13.2, “Wet Brakes”

Question 4

For cargo that can be inspected, when must its securement be rechecked during a trip?

  1. A Only before the vehicle first moves
  2. B After every break taken while driving
  3. C Only when transporting hazardous materials
  4. D Only after six hours or 300 miles

Correct answer: B – After every break taken while driving

Inspectable cargo and its securement devices must be checked within the first 50 miles after beginning the trip. They must be rechecked after three hours or 150 miles of driving, whichever occurs first, and after every driving break. Federal rules provide exceptions when a sealed vehicle cannot be opened or when the cargo's loading makes inspection impracticable.

Source: Idaho Commercial Driver’s License Manual — § 3.1, “Inspecting Cargo”, 49 CFR § 392.9(b) — Inspection of Cargo, Cargo Securement Devices and Systems

Question 5

Which driving abilities are affected first as alcohol begins influencing the brain?

  1. A Judgment and self-control
  2. B Kidney function
  3. C Physical coordination only
  4. D Large-muscle control only

Correct answer: A – Judgment and self-control

The first part of the brain affected by alcohol controls judgment and self-control. Impairment in this area can keep a drinker from accurately recognizing how affected they have become. As blood alcohol concentration rises, coordination, vision, muscle control, and other abilities needed for safe driving become increasingly impaired.

Source: Idaho Commercial Driver’s License Manual — § 2.22.1, “Alcohol and the Brain”

Question 6

If your commercial vehicle stops on a one-way or divided highway in Idaho, where should three reflective triangles be placed?

  1. A About 10, 100, and 200 feet toward approaching traffic
  2. B About 25, 100, and 250 feet toward approaching traffic
  3. C About 50, 100, and 300 feet toward approaching traffic
  4. D About 75, 100, and 400 feet toward approaching traffic

Correct answer: A – About 10, 100, and 200 feet toward approaching traffic

Federal rules require one warning device on the traffic side approximately 10 feet from the stopped vehicle in the direction of approaching traffic. The other devices are placed approximately 100 feet and 200 feet toward approaching traffic. Different placement patterns apply on undivided highways and near hills, curves, or other obstructions.

Source: Idaho Commercial Driver’s License Manual — § 2.5.2, “Warning Devices”, 49 CFR § 392.22(b)(1) — Emergency Signals; Stopped Commercial Motor Vehicles

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