Tractors without semi-trailers are referred to as "bobtail tractors." Bobtail tractors are difficult to operate and drivers must exercise caution.

A tractor without a semi-trailer

A tractor with two semi-trailers

A tractor that travels faster than the speed limit

When any vehicle goes around a corner, the rear wheels follow a different path than the front wheels. This is called off-tracking. The degree of off-tracking will be greater on long vehicles than on short vehicles.

Follow a different path than the front wheels.

Follow the same path as the front wheels.

Follow a different path than the front wheels.

Should not be a concern to the driver.

The tractor protection valve keeps air in the trailer's braking system should the trailer break away or develop a leak. A loss of air pressure in the emergency line will cause the tractor protection valve to open and the emergency trailer brakes to activate.

The tractor protection valve to close.

The service brakes to activate.

The tractor protection valve to close.

The rear trailer to detach from the combination.

The suspension springs to extend.

To reduce the risk of a surge in a tank vehicle, slow or stop while keeping a steady pressure on the brakes and do not release the brakes too early. Brake well in advance of a stop and increase your following distance.

Release the brakes too quickly.

Keep a steady pressure on the brakes.

Brake well in advance of a stop.

Release the brakes too quickly.

The tractor protection valve keeps air in the trailer's braking system should the trailer break away or develop a leak. A loss of air pressure in the emergency line will cause the tractor protection valve to open and the emergency trailer brakes to activate.

The tractor protection valve will close.

The service brakes will activate.

The tractor protection valve will close.

The rear trailer will detach from the combination.

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.

Are more likely to roll over than empty rigs.

Are less likely to roll over than empty rigs.

Are more likely to roll over than empty rigs.

Are just as likely to roll over as empty rigs.

Vehicles with trailers are vulnerable to rollover due to the "crack-the-whip" effect, which is caused by rearward amplification.

The cause of the "crack-the-whip" effect.

The amount of noise projected to the rear of a vehicle.

The cause of the "crack-the-whip" effect.

The number of trailers that can be pulled by a tractor.

Combination Vehicles Practice Test | Tennessee 2025 #1

Train for FREE online with our Tennessee 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 TN 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

Combination Vehicles Practice Test | Tennessee 2025 #1

1 . What is a bobtail tractor?

2 . When a vehicle goes around a corner, the rear wheels:

3 . A loss of air pressure in the emergency line will cause:

4 . To control surge when stopping, you should not:

5 . If the emergency air line loses pressure:

6 . Fully-loaded rigs:

7 . Rearward amplification refers to:

Search the best driving school in your neighbourhood

Wait, before you go