CDL Practice Test


Below are practice questions for the Iowa CDL test. The site is free and you are able to take the practice test as many times as you need to as you prepare to obtain your Iowa CDL. The questions and answers covered in these Iowa practice CDL tests are taken from the Iowa DOT CDL manual. You will be presented with 40 questions and you must answer 34 questions correctly to pass. There is a 50-minute time limit. You may not go back once you answer a question. Click the "Start Test
" button below to begin.

1 / 40

The most dangerous time during the school bus ride is:

2 / 40

When is it acceptable for non-hazardous materials to be described by hazard class words or identification numbers?

3 / 40

What might happen if you swing wide to the left before you turn right?

4 / 40

You should have the fifth wheel plate greased as recommened because:

5 / 40

When must a driver’s inspection report be completed?

6 / 40

When should you check your mirrors for a lane change?

7 / 40

Your rig should be parked on__to uncouple double trailers.

8 / 40

To avoid rollover when going through a curve, the best thing to do is:

9 / 40

What is most likely to occur when driving double and a set of trailer wheels goes into a skid?

10 / 40

What does it mean when the safety valve releases air?

11 / 40

Which trailer should be the first one after the tractor?

12 / 40

A shipper’s certification is best described as _____.

13 / 40

You should turn off your engine when loading flammable liquid unless:

14 / 40

Which trailer is more likely to roll over when pulling 3 trailers?

15 / 40

What is the value of the overhead rear-view mirror inside of the bus?

16 / 40

What does the amount of liquid allowed in the tank depend on?

17 / 40

To be sure that air is supplied to the second trailer:

18 / 40

The most stable tanker shape is:

19 / 40

What should you do if you start a trailer skid?

20 / 40

Select the true statement:

21 / 40

What is a passive railway crossing?

22 / 40

On a bus, you may sometimes haul small-arms ammunition, emergency shipments of drugs, or hospital supplies. The total weight of all such hazardous materials must not be greater than:

23 / 40

Puddles or dripping fluids from the underside of the transmission and engine may indicate:

24 / 40

What is the most important reason for doing a vehicle inspection?

25 / 40

You should____to check the free play of manual slack adjusters on S-Cam brakes.

26 / 40

Select the factor that has no effect on how much liquid you can carry:

27 / 40

How should the hand valve be used?

28 / 40

What is the best way to stop all skids?

29 / 40

The 3 parts of the air brake system are: service brakes, parking brakes, and ____.

30 / 40

At around____the governor allows the air compressor to start pumping again:

31 / 40

Select the true statement about empty trucks:

32 / 40

An air system that is fully charged will typically have ___ psi of pressure.

33 / 40

Which of the following statements about downshifting is NOT true?

34 / 40

How should you inspect a converter dolly?

35 / 40

You must carry a gas mask with you when transporting:

36 / 40

A "transport index" relates to products that are:

37 / 40

How do you secure a second trailer to your combination vehicle?

38 / 40

Remember to____when connecting the converter dolly to the rear trailer.

39 / 40

While driving on a clear night with low beam headlights, you should be able to stop within:

40 / 40

You should expect____when backing a tractor under a trailer.

Your score is

The average score is 62%

5/5 - (1 vote)

CDL Category Practice Tests

CDL Practice Test

How To Get An iowa Commercial Drivers License

Individuals may apply for their CDL starting at age 18. To be eligible for interstate driving as well as HazMat and Doubles/Triples applicants must be 21 years of age or older. All individuals applying for an Iown CDL must present a Medical Examiner’s Certificate according to the United States Federal Regulations.

If any one of the descriptions below is true about an applicant, they will be disqualified from receiving their CDL.

  • Driver posses more than one driver’s license.
  • Driver was convicted of driving under the influence in the past 24 months.
  • Driver has a suspended, denied, canceled, or revoked driver’s license.

H – Hazardous Materials
N – Tank Vehicle
T – Doubles/Triples
X – Hazmat and Tank Comb
P – Passenger Vehicle
S – School Bus

Drivers must take a knowledge test as well as a practical skills test to showcase their knowledge of commercial driving laws and their ability to operate a commercial vehicle.

Hit the Open Road

iowa CDL License Test Tips

Applicants must complete a general knowledge test to display their understanding of commercial driving laws. The general knowledge exam is comprised of 50 questions. Those seeking a Class A CDL will need to complete an additional 20 question test on combination vehicles. Applicants seeking additional endorsements will need to take an additional test on the endorsement topic. The Passenger, Tank, and Doubles/Triples Endorsements are 20 question tests. Removing the Air Brake Restriction, the Iowa Operator and School Bus Endorsements are 25 questions. The Hazmat Endorsement is a 30 question test. All applicants must pass the respective assessments with a score of 80 percent or better to receive their Iowa CDL permit.

A skills assessment is required of all applicants. This assessment is comprised of three parts, which are the pre-trip inspection, basic controls skills, and on-road driving. Individuals applying for their P and S endorsements will be required to take the skills test in the respective vehicle for their endorsement.

Additional Information

Information on the Iowa Department of Transportation

The Iowa Department of Transportation administers CDL requirements and testing in Iowa. To get more information contact them via:


Phone:  515.239.1101


Additional Iowa CDL Helpful Links

Please use the links below to access more valuable Iowa CDL testing resources and to learn more about practice driving tests for the state of Iowa.