LA CDL Combination Practice Test (2024)

1. When checking the air and electric lines to the trailer, be sure that the air lines are properly connected to the gland hands, and are:

secured with enough slack for turns.
properly greased.
secured with enough air leaks for turns.
None of the above.

2. The center of gravity of a trailer should be:

3. By pushing the trailer air supply control knob in, you:

keeps air in the tractor or truck brake system.
supply the trailer with air.
supply the tires with air.
shut the air off and put on the trailer emergency brakes.

4. You should test the coupling by:

pulling against the pin of the second semitrailer.
applying the parking brakes so the rig will not move.
disconnect the safety chains.
locking the pintle hook.

5. When should you use chocks to park a trailer without spring brakes?

6. The best way to test the trailer service brakes is to:

put the handbrake on when there are no vehicles around you.
pull forward quickly, then apply the trailer brakes with your hand control.
accelerate to the maximum possible speed, then apply the trailer brakes fully.
None of the above.

7. If you discover a fire, before opening trailer doors you should:

have a helper open the doors.
feel the doors to see if they are hot.
use the fire extinguisher on the doors.
All of the above.

8. Which of the following is NOT TRUE? When you drive a tractor-trailer combination with ABS, you should:

use only the braking force necessary to stop safely.
brake the same way, regardless of whether you have ABS on the tractor, the trailer, or both.
monitor your tractor and trailer as you slow down, and if it is safe to do so, back off the brakes to stay in control.
drive slower to keep your vehicle in a straight line.

9. The emergency air line does NOT:

cause the tractor protection valve to close when the emergency line loses pressure.
supply air to the trailer air tanks.
control the emergency brakes on combination vehicles.
pump air into the relay valves, allowing the trailer brakes to be applied more quickly.

10. When you are uncoupling a loaded trailer, lower the landing gear until:

the tractor frame is under the trailer.
makes contact with the ground, and leave the trailer off the fifth wheel.
it makes firm contact with the ground.
the pressure in the system is above 55 psi.

CDL COMBINATION PRACTICE TEST (LA)