iowa
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 minimum tread depth for steering axle tires is:

None of the answers listed

2/23 inch

14 mm

4/32 inch

2 / 40

Select how you would check the truck's slack adjusters.

listen for any strange noises while applying pressure to the brake pedal

brake hard after accelerating

while wearing gloves, pull hard on each slack adjuster that you can reach

all of these answers are correct

3 / 40

When driving with multiple trailers, which one should be right behind the tractor?

the trailer with the smallest road

the trailer with the heaviest load

the trailer longest in length

the trailers shortest in length

4 / 40

Where is compressed air stored?

in the storage tank

in the hose lines

in the compartment for the engine

in the gasoline tank

5 / 40

A baffled tanker has:

Separate compartments inside the trailer.

No side to side surge.

Balls floating in it to increase the speed of the liquid movement.

Bulkheads with holes that allow liquid to flow through it.

6 / 40

What is the service air line controlled by?

the relay vavle by sending air pressure from the trailer air tank to the trailer brake chambers

the pressure applied to the trailer hand brake or by the foot brake

all answers listed

the relay valve that connects the trailer air tanks to the trailer air brakes

7 / 40

You must first______to supply air to the trailer.

push in the tractor protection valve

turn off the engine so you can hear the brakes

pull out the tractor protection valve

cross the air lines to check for the presence of leaks

8 / 40

A safe haven is:

A place that has been approved to park unattended vehicles carrying explosives.

A place to stay once you have reported your company for illegal activity.

A place where it is safe to dump any kind of hazardous materials.

The slang term for the last stop at the end of your driving day when carrying hazardous materials.

9 / 40

It takes special care to drive tankers with liquid in them because:

The movement of the liquid even when the truck is stopped.

The low center of gravity of the load.

The baffles create odd rocking motions.

The high center of gravity of the load.

10 / 40

Which of the following is a recommended procedure when unloading the students?

Let the students begin moving to the front of the bus before it's fully stopped to maximize efficiency.

Tell students to remain seated until they are told to exit.

Position yourself outside of the bus in front of crossover mirror to supervise unloading.

Put the transmission in neutral gear and put on the brakes.

11 / 40

You must keep shipping papers describing hazardous materials ______.

within 100 feet of the hazardous materials at all times

in a pouch on the drivers door or in the overhead compartment above the driver’s seat only

in a pouch on the driver’s door or in clear view within immediate reach while the seat belt is fastened while driving on the driver’s seat when out of the vehicle

with the bills of lading

12 / 40

Which of the following is NOT an important reason to look far ahead when you are driving?

look for vehicles coming into your lane

look for brake lights from slowing vehicles

determine if there are any upcoming traffic lights that might require you to stop

determine if there are any hills coming up

13 / 40

For what reason do you keep the starter switch key in your pocket during the pre-trip inspection?

you will need it to inspect the trailer

so no one moves the vehicle while you are inspecting underneath it

so you don't lose it

you will need it to open the side box

14 / 40

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

the trailer's air tank will leak through the one line

the emergency tractor brakes will activate

you will come to a complete stop

nothing will occur until you try to use the brakes

15 / 40

Mirrors with a convex surface or "spot" mirrors _____.

they show a larger area than flat mirrors so do not need to be checked as often

make things look farther away and smaller than they actually are

are illegal in most states

make things look closer and larger than they actually are

16 / 40

You should follow the posted speed limits for curves and be aware of:

A rollover may occur even when driving at the posted speed limit.

The posted speed limit may be too high for safety.

The higher center of gravity on a tank truck.

All answers listed.

17 / 40

On tandem axle for trailers, the sliding mechanism and locking device is:

Fifth wheel

Tandem release (locking pin/arm)

Air brake system

Metal frame

18 / 40

The front trailer supports should be____before driving away.

raised fully and the crank handle secured in its bracket

raised 1/3 of the way with the crank handle secured in its bracket

raised 1/2 way with the crank handle secured in its bracket

3 turns down from the top and the crank handle secured in its bracket

19 / 40

What does the air compressor governor control?

when air pressure is applied to the brakes

when the valve system releases pressure

when air is pumped into the air tanks

when the air is taken out of the hoses

20 / 40

The longest crack that brake or disc drums can have is:

1/2 inch across in a straight line.

None of the answers listed.

Cracks are not permitted.

1/2 the width of the friction area.

21 / 40

The method used to make sure the spring brakes will come on automatically is to:

Apply pressure on and off the brake pedal to decrease the air tank pressure while driving at a high a speed. The parking brake knob should pop out when the air pressure meets to the manufacturer’s specification.

Apply pressure on and off the brake pedal to decrease the air tank pressure. The parking brake knob should pop out when the air pressure meets to the manufacturer’s specification.

Apply pressure on and off the brake pedal to increase the air tank pressure. The parking brake knob should pop out when the air pressure meets to the manufacturer’s specification.

Apply pressure on and off the brake pedal to decrease the air tank pressure. The parking brake knob should pop out when the air pressure drops to 120 psi.

22 / 40

If you are drowsy, you should _____ before you drive.

do a little exercise

get sleep

drink coffee

take a cold shower

23 / 40

The minimum tread depth for tires other than the front tires is ____.

3/32

1/32

2/32

4/32

24 / 40

When this item is missing or loose, movement may occur between the fifth wheel assembly and the frame.

Tandem release arm

Locking jaw

Locking pins

Lug nuts

25 / 40

The best way to describe a dual air brake system is:

there are 2 separate air brake systems that supply air to the trailer if there is one

all of these answers are correct

there are 2 separate air brake systems that have their own hoses, lines etc

there is a primary and secondary system that is 2 separate air brake systems

26 / 40

When should the trailer hand valve be used?

to test the trailer brakes

all answers listed

when driving at highway speeds

when parked in a service lot

27 / 40

What is the earliest way to notice a trailer skid?

you can feel a jerk in the back of the tractor

you can hear the tires squealing

you can feel it pulling your steering wheel

you can see it in your mirrors

28 / 40

When does your vehicle's single brake system need an adjustment?

when the governor stops between 75-90 psi

if the pressure builds from 50 to 75 psi in less than 3 minutes

when the pressure builds from 85 to 100 psi in less than 1 minute

if the compressor cuts out at between 70 and 90 psi

29 / 40

Select the true statement about emergency steering and tankers:

Do not apply the brakes when making quick movements of the steering wheel.

None of the answers listed.

It is easier to counter steer than other vehicles.

Have a firm grip on the steering wheel before making quick movements of the steering wheel.

30 / 40

How do you determine if slack adjusters need to be adjusted?

release the parking brakes and service brakes

pull out the automatic slack adjustment control knob

activiate the parking brake and service brake

release the parking brakes and activate the service brakes

31 / 40

If you have riders on board, you must never refuel:

Unless on a scenic tour bus.

In a closed building.

With any window open.

At any time.

32 / 40

What is the safest way to stop unruly behavior on the bus?

pull off the road in a safe location, secure the bus, stand up, and tell the students what behavior you expect of them

have the unruly students move to the front of the bus

keep checking the rear view mirror so you can see what happened and report to the principal

yell loudly for the students to sit down and behave themselves

33 / 40

While completing the 2nd component of the air brake check you are required to turn the electrical power on, begin fanning off the air pressure by rapidly relasing and apply the foot brake and _____.

a low air warning device should sound before the air pressure drops below 60 psi

the tractor protection valve and parking brake valve should pop out before air pressure falls below 60 psi for combination vehicles

none of the answers listed

a low air warning device should sound before the air pressure drops below 40 psi

34 / 40

Select the true statement about handling triples and doubles:

because of the crack the whip effect, the rear trailer of a 100-foot triple is less likely to tip over

due to off-tracking, a triple bottom rig can come to a stop faster than a 5-axle tractor

triples and doubles handle the same as singles

a tip over of the rear trailer can occur due to sudden movements of the steering wheel

35 / 40

Select the true statement in regards to if a glad hand on the blue air line is missing a seal.

you should remove one from the red air line to use as a temporary replacement

there may be a service line air leak

it is not a big problem

there may be an emergency line air leak

36 / 40

Select the item that is not checked in the engine compartment:

The level of the oil

The coolant level

The oil pressure

The power steering fluid

37 / 40

You should_____when an emergency requires you to quickly stop your tanker.

keep a firm pressure on the brake pedal

use stab or controlled braking

use the emergency brakes only

turn off the abs and brace for impact

38 / 40

The shipping papers for hazardous materials can be found:

Any of the above locations.

On the driver's seat when out of the vehicle.

In clear view, within reach while driving.

In a pouch on the driver's door.

39 / 40

Operating a motor vehicle with the intent of doing harm to others or physically assaulting a driver or their vehicle is known as?

tailgating

aggressive driving

defensive driving

road rage

40 / 40

Select the factor that is known to cause brakes to fail or fade. (more than one answer may be correct, but select only one)

brakes that are not aligned properly

tire retread that is mismatched

excessive heat from extensive use

when using the engine brake more than the brakes

Your score is

The average score is 0%

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.

Endorsements
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:

Website: https://iowadot.gov/DriversVehicles#CommercialDrivers

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.

iowa CDL Practice Test