Combination #1
Combination Vehicles Practice Test | Iowa 2025 #1 Page 3 of 3
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.
20
16
20
15 . Having anti-lock brakes on only one axle:
If a vehicle has anti-lock brakes on just one axle, the driver will still have more control during braking than they would without any anti-lock brakes.
16 . A driver should test the tractor protection valve by:
You should test the tractor protection valve by allowing the air supply to properly charge, turning off the engine, then releasing air from the system by pressing the brake pedal several times. The tractor protection valve should move into its emergency position when psi drops to an unsafe level.
17 . A trailer that is too high:
Before coupling together a tractor and a trailer, you should make sure the trailer is at the proper height. If the trailer is too low, the trailer nose may be damaged. If the trailer is too high, it may not be able to couple correctly.
18 . The trailer hand valve should be used:
The trailer hand valve (also referred to as the "trolley valve" or "Johnson bar") works the trailer brakes and should be used only when testing them. Using the trailer hand valve while driving could result in a skid.
19 . Older trailers are not equipped with spring brakes. This means that if the air supply for a vehicle's air braking system leaks away:
Older trailers do not have spring brakes. This means that if the air supply in an older trailer's air tank has leaked away, there will be no working brakes connected to the trailer and its wheels will turn freely.
20 . If the emergency air line loses pressure:
The emergency air line controls the emergency brakes on a combination vehicle. A loss of air pressure in the emergency line will cause the emergency trailer brakes to activate.
Search the best driving school in your neighbourhood
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.
