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

These tires should have a minimum tread depth of 4/32 inches.

2 / 40

What is the service air line controlled by?

3 / 40

Which signals may be used to warn of a stopped vehicle that contains explosives?

4 / 40

You must keep shipping papers describing hazardous materials ______.

5 / 40

How often should you check the cargo you are transporting?

6 / 40

Do empty trucks have the best braking?

7 / 40

Which of the following is the most important reason for doing a pre-trip inspection?

8 / 40

What are shippers trying to accomplish when they package the material?

9 / 40

A vehicle placarded for Division 1.1, 1.2, or 1.3 explosives:

10 / 40

Secure baggage and freight in ways that avoid damage and:

11 / 40

Which of these statements about speed management and braking is true?

12 / 40

The bus driver must accept responsibility for supervising and controlling students while on the bus route. Who is the person in charge?

13 / 40

Select which vehicles are required to have a low air pressure warning signal:

14 / 40

If you must stop on the shoulder of the road, you should place warning devices at all of the following places except...

15 / 40

How much space should you see between the lower and upper fifth wheel when checking the coupling of a converter dolly?

16 / 40

Five hazard classes that require placarding in any amount are ______.

17 / 40

Select the false statement about tractor protection valves.

18 / 40

Select the statement that is true in regards to quick steering movements and triple/double trailers:

19 / 40

For Division 1.1 or 1.2 Explosives A, should the floor liner required be stainless steel?

20 / 40

The two other places where the hazardous identification number must appear are:

21 / 40

When approaching railroad tracks, stop your bus:

22 / 40

Drivers placard their vehicle to _____ the risk.

23 / 40

Liquid surge affects the handling of a tanker by:

24 / 40

What is most likely to occur when driving a tanker truck and the front wheels begin to skid?

25 / 40

In what location must you keep your shipping papers which describe any hazardous materials?

26 / 40

If hazardous material is spilling from your vehicle, do not move your vehicle:

27 / 40

The bolst, brackets, or bushings that attach the air bag and/or spring to the vehicle and axle frame are _____.

28 / 40

The brake pushrod should not move more than____for manual slack adjusters.

29 / 40

How should you know when to shift?

30 / 40

Water is drained from the compressed air tanks because:

31 / 40

Bus drivers must have a CDL if they drive a vehicle:

32 / 40

Where is compressed air stored?

33 / 40

The best way to test the low air pressure warning signal is to:

34 / 40

If you double your speed, what will happen to your stopping distance?

35 / 40

When not towing a trailer, why should the tractor glad hands be locked?

36 / 40

Tankers used to transport hazardous materials on vehicles must be marked with:

37 / 40

What product is typically carried in a liquid tank trailer without baffles?

38 / 40

Which of the following statements about overhead space is true?

39 / 40

This gauge will indicate if the generator or alternator is charging:

40 / 40

What will happen right away should the service air line come apart but the emergency line is intact while driving a combination vehicle?

Your score is

The average score is 55%

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.