20 Tests

CDL Combination Vehicles Practice Test Online | Oklahoma 2021

Train for FREE online with our Oklahoma 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 OK combination license in 2021, practice as much as.. Read More

Train for FREE online with our Oklahoma 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 OK combination license in 2021, 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.

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1 . If color-coded, which color is used to identify emergency, or supply, lines?

Air lines are sometimes color-coded to help drivers avoid mistakes when coupling glad hands. Typically, blue is used for service lines and red is used for emergency lines.

2 . 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.

3 . All trailers made after ____ must be equipped with Anti-Lock Braking Systems (ABS).

All trailers and converter dollies manufactured on or after March 1, 1998 must have Anti-Lock Braking Systems (ABS).

4 . When coupling a trailer, you should:

When coupling air brake hoses, you should make sure the proper pairs of gland hands are connected. They are sometimes color-coded to help drivers avoid mistakes. Typically, blue is used for service lines and red is used for emergency lines.

5 . When coupling:

Incorrect coupling and uncoupling of combination vehicles can have extremely dangerous consequences.

6 . When the wheels of a trailer lock up:

A trailer may swing out and strike other vehicles if its wheels lock up. This is especially likely with lightly-loaded trailers.

7 . When should the trailer hand valve be used?

The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. It should be used only to test the brakes. Using it while a vehicle is in motion could cause a skid.

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