FREE CDL Combination Vehicles Practice Test Online | Nebraska 2024 Page 2 of 4
Train for FREE online with our Nebraska 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 NE 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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7 . What is a tractor protection valve?
A valve that prevents the trailer from accidentally being released
In a combination vehicle with air brakes, the tractor protection valve keeps air in the tractor or truck brake system in the event of the trailer breaking away or developing a leak.
8 . An air supply control lever should be in its "normal" position when you are:
Using your spring brakes.
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.
9 . Using the trailer hand brake while experiencing a trailer jackknife will:
Continue the skid.
If you are experiencing a trailer jackknife, you can help your tires regain traction by releasing the brakes. Using a trailer hand brake while experiencing a skid will only cause the skid to continue.
10 . Trailers with low underneath clearance can present challenges when driving over:
Railroad-highway crossings may be difficult to cross when pulling a trailer with a low underneath clearance. In particular, both low-slung units and single-axle tractors pulling long trailers are especially challenging to drive over raised crossings.
11 . 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.
12 . To lower the risk of a rollover, you should:
Stack the cargo as high as possible.
