Before a trip, you should ensure that air reaches all air brakes on all trailers by opening up the rear emergency line and service line shut-off valves and listening for escaping air. Close both shut-off valves before beginning to drive.

Close the emergency line valve.

Leave the service line valve open.

Close the emergency line valve.

When starting a trip, be sure that all shut-off valves are in the open position, except for the last valves on the rear trailer. It is important that air reaches the brakes on all trailers and that it is not able to escape from the back of the vehicle.

Rear service line shut-off valve

Rear supply line shut-off valve

Tractor protection controls in older vehicles may be operated by levers instead of knobs. If an air supply control is set in its "emergency" position, the air supply will be stopped and the trailer emergency brakes will be applied.

The trailer emergency brakes will be applied.

The vehicle will increase speed.

The trailer emergency brakes will be applied.

The air supply to the trailer will increase.

The easiest way to become aware that your trailer has begun to jackknife is to observe it in your mirrors. Checking your trailer in your mirrors will also allow you to spot any skidding at the earliest possible moment.

Checking the trailer in your mirrors.

Trailers can overturn as a result of the "crack-the-whip" effect. The last trailer in a combination is the most prone to tip over due to this effect. Drivers should be aware of the rearward amplification of their specific vehicles and drive accordingly.

Be more effective than braking.

Combination Vehicles Practice Test | Maine 2024 #1 Page 2 of 3

Train for FREE online with our Maine 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 ME combination license in 2024, 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 | Maine 2024 #1 Page 2 of 3

8 . Trailers built before ____ are not required to have spring brakes.

9 . Before beginning a trip, you should:

10 . During a trip, the ____ should be open.

11 . If an air supply control is in its "emergency" position:

12 . After completing a pre-trip inspection, you should ensure that the:

13 . The best way to recognize that your trailer has started to skid is by:

14 . The "crack-the-whip" effect can:

See the exact questions that will be on the 2024 DMV exam.

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