Prevent air from escaping air brake systems.

Prevent air from entering air brake systems.

Override vehicles that are out of control.

Are more likely to roll over than empty rigs.

Are less likely to roll over than empty rigs.

Are just as likely to roll over as empty rigs.

Louisiana CDL Combination 1 - DMV Written Test Questions with Answers

Q.1

Shut-off valves:

Prevent air from escaping air brake systems.
Prevent air from entering air brake systems.
Override vehicles that are out of control.

Q.2

Fully-loaded 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.

Q.3

The trailer hand valve should not be used while you are driving because:

It will disconnect from the vehicle.
You will stop the vehicle too quickly.
It can cause a skid.

Q.4

Older trailers are not equipped with spring brakes. This means that if the air supply for a vehicle's air braking system leaks away:

The trailer will stop normally.
The trailer will not have brakes.
The trailer will speed up.

Q.5

If a load is placed on one side of a trailer, the trailer:

May lean during turns.
May add extra support during turns.
May be easier to steer during turns.

Q.6

If you are backing and become unsure about your path of travel, you should:

Continue backing.
Stop and get out to look.
Continue backing, but more slowly than before.

Q.7

Rollovers happen when:

You drive too slowly.
You are stopped.
You take a turn too fast.

Q.8

Bobtail tractors are ____ to stop than tractors attached to full semitrailers.

Quicker
Easier
More difficult

Q.9

What is the Johnson bar?

A hand valve that works the trailer brakes
A valve that indicates the fuel level
A valve that limits the amount of cargo

Q.10

Combination vehicles are usually:

Easier to drive than single commercial vehicles.
Lighter than single commercial vehicles.
More difficult to drive than single commercial vehicles.

Q.11

If a parked trailer does not have spring brakes, you should keep the trailer from moving by:

Having the vehicle parked against a wall or other vehicle.
Using chock blocks.
Parking on a slight incline.

Q.12

If color-coded, which color is used to identify service lines?

White
Yellow
Blue

Q.13

When coupling a trailer:

Make sure to couple the proper glad hands.
Glad hands can be connected to any other glad hands.
Only one set of glad hands should be connected.

Q.14

Place the trailer air supply control in its "emergency" position to test:

The trailer emergency brakes.
A coupling device.
The anti-lock brakes.

Q.15

If a trailer begins to jackknife, the driver:

Should not apply the trailer hand brake.
Should firmly apply the brakes.
Can straighten the trailer with the parking brake.

Q.16

Pushing in the trailer air supply control will:

Supply the trailer with air.
Deactivate the air brakes.
Prevent the vehicle from skidding.

Q.17

The service air line is often controlled by the foot brake and is attached to the ____ valves.

Relay
Supply
Emergency

Q.18

Trailers with low underneath clearance can present challenges when driving over:

Bridges.
Railroad tracks.
Overpasses.

Q.19

To prevent a rollover, cargo should be:

Loaded with most weight on the driver’s side of the trailer.
Placed near the rear of the trailer.
Spread out in the trailer.

Q.20

Combination vehicles need extra space on the road because they:

Drive more slowly than other commercial motor vehicles.
Are heavier than other commercial motor vehicles.
Need more space to turn and stop than other commercial motor vehicles.