Combination Vehicles Practice Test | Iowa 2025 #1

Train for FREE online with our Iowa CDL combination vehicle test. The official exam test consists of several obligatory parts, with all of them checking your knowledge of different blocks of road rules. If you need to obtain a IA combination license in 2025, practice as much as possible. Free sample tests published on our website will help you check and improve your knowledge and boost your grades. Please bear in mind that DMV requirements for issuing a combination license may vary from state to state.

Number of Question 20

Passing Score 16

Number of Tests 20

1 . The best way to recognize that your trailer has started to skid is by:

Seeing other drivers' faces.

Checking the trailer in your mirrors.

Feeling the trailer move.

The easiest way to become aware that your trailer has begun to jackknife is to observe it in your mirrors. Checking your trailer in your mirrors will also allow you to spot any skidding at the earliest possible moment.

2 . In a vehicle equipped with an automatic tractor protection valve, the valve will pop out when air pressure drops to a level between:

20 and 45 psi.

75 and 105 psi.

50 and 65 psi.

In vehicles equipped with an automatic tractor protection valve, the valve will pop out if air pressure drops to a level between 20 and 45 psi. When the valve pops out, the protection valve will close, stopping the flow of air.

3 . Fully-loaded rigs:

Usually are very responsive to steering.

Are more likely to roll over than empty rigs.

Can stop quickly.

Fully-loaded rigs are more vulnerable to rolling over than empty rigs because the weight of the cargo gives the vehicles higher centers of gravity.

4 . Keeping cargo centered on a rig can:

Help you drive faster.

Prevent a rollover.

Make turns more dangerous.

A rollover is more likely if cargo is unevenly loaded in a rig. To help prevent a dangerous rollover, it is important to keep a load as centered on the rig as possible.

5 . When you are pulling a trailer, the air supply control lever should be in its ____ position.

Emergency

Supply

Normal

Tractor protection controls in older vehicles may be operated by levers instead of knobs. If an air supply control is set in its "normal" position, it is properly set for you to pull a trailer.

6 . Trailers built before ____ are not required to have spring brakes.

1985

1975

1999

Trailers built before 1975 are not required to have spring brakes. When parking a trailer without spring brakes, be sure to use wheel chocks to prevent the trailer from rolling.

7 . What does an Anti-Lock Braking System (ABS) do?

It allows a vehicle's wheels to lock up.

It prevents a vehicle's wheels from locking up.

It makes turning a vehicle easier.

An Anti-Lock Braking System (ABS) helps prevent wheel lockup during hard braking. If ABS detects impending lockup, it reduces braking pressure to a safe level.

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2025 Iowa | Frequently Asked Questions

To secure a CDL Doubles/Triples endorsement in Iowa, you must first possess a valid Commercial Driver's License (CDL). Then, you need to pass the Doubles and Triples Endorsement Knowledge Test. This test covers the specifics of driving double and triple trailers, coupling and uncoupling, and inspecting doubles and triples. Remember, practice makes perfect.

To obtain a CDL Doubles/Triples license, you initially need a Commercial Driver's License (CDL). Then, you must pass the Doubles/Triples Endorsement Knowledge Test. The test covers topics like handling, coupling & uncoupling, and inspecting double and triple trailers. Studying the state's CDL manual and taking practice tests can help ensure success.

While Iowa doesn't specifically require specialized training to obtain a CDL Doubles/Triples endorsement, it's highly recommended. The endorsement requires passing a knowledge test on handling, inspecting, and coupling/uncoupling double and triple trailers. Studying the state's CDL manual and gaining practical experience through training programs can significantly improve your chances of passing the test.

Yes, to obtain a CDL Doubles/Triples endorsement, you are required to pass the Doubles/Triples endorsement knowledge test. This exam covers specific topics related to handling double and triple trailers, including coupling and uncoupling, inspecting doubles and triples, and pulling double/triple trailers. The test does not include a skills or driving test.

The CDL Doubles/Triples endorsement test is a written knowledge test, not a skills test, so you won't perform any driving maneuvers. The test covers information on handling, inspecting, and coupling/uncoupling double and triple trailers. It's important to have a good understanding of these areas to pass the written test. Practical skills are typically developed during on-the-job training after receiving the endorsement.

No, it's not permissible to operate double or triple trailers without a valid CDL Doubles/Triples endorsement in Iowa. This endorsement is required by federal and state law for any driver who intends to operate a vehicle towing two or three trailers. Driving without the proper endorsement can result in penalties, including fines and suspension of your commercial driving privileges.

You can add the CDL Doubles/Triples endorsement to your existing Commercial Driver's License. You don't need to initiate a new application for a CDL. However, you will need to pass the Doubles/Triples written knowledge test and pay any required fees to add the endorsement to your current CDL.

Yes, there are limitations for drivers with a CDL Doubles/Triples endorsement. One major constraint is the Gross Combination Weight Rating (GCWR) of 26,001 pounds or more, provided the GVWR of the vehicle(s) being towed is more than 10,000 pounds. Additionally, drivers must adhere to specific safety regulations related to coupling and uncoupling, inspecting, and driving double/triple trailers.

In Iowa, the maximum length for a double trailer is 81.5 feet. For triple trailers, it's 100 feet. The maximum weight for any vehicle or combination is 80,000 pounds gross weight depending on axle and bridge formula. However, specific weight limits can also be determined by the Federal Bridge Gross Weight Formula. Always check local and state laws for specific restrictions.

Yes, there are specific safety regulations for driving double/triple trailers. Drivers must adhere to guidelines concerning coupling and uncoupling, inspecting the trailers, and maintaining safe following distances. Other regulations include not driving in the left-most lane on interstates, obeying speed limits, and securing cargo properly. These regulations aim to ensure the safety of the driver and other road users.