The DMV doubles triples practice test will examine your knowledge of pulling double/triple trailers, coupling and uncoupling, inspecting doubles and triples, and checking air brakes. In order to receive your Doubles and Triples endorsement, it is required that you pass the state’s official CDL written Knowledge exam.
For all brakes to work on a triple combination, you must have air supply...?

Question 1 of 30

When uncoupling a rear trailer, you should remove some weight from the dolly by...?

Question 2 of 30

Converter dollies are connected to front trailers with a...?

Question 3 of 30

Once you have coupled your rear trailer, you should test the coupling by...?

Question 4 of 30

When uncoupling a rear trailer, your rig should be parked in a straight line on...?

Question 5 of 30

When testing trailer service brakes, you should use...?

Question 6 of 30

On double and triple combinations, you must make sure that which of these is secure?

Question 7 of 30

On a triple combination, the shutoff valves on the rear of the last trailer should be...?

Question 8 of 30

If your tractor protection valve doesn't work properly, then if an air hose starts to leak what could happen?

Question 9 of 30

If the fifth wheel on a coupling is too far forward, the tractor frame may hit...?

Question 10 of 30

The coupling between a rear trailer and a dolly should have a space between the upper and lower fifth wheels of...?

Question 11 of 30

If your converter dolly has to be moved over a distance to bring it to your semitrailer, you should...?

Question 12 of 30

In the coupling system, the locking jaws should be fixed around...?

Question 13 of 30

Light cords should be attached to...?

Question 14 of 30

How many different ways of coupling and uncoupling trailer combinations are there?

Question 15 of 30

When checking the fifth wheel, you should make sure that it has enough...?

Question 16 of 30

The final procedure when connecting a rear trailer is to...?

Question 17 of 30

In normal operation, trailer service brakes should be operated by...?

Question 18 of 30

If the converter dolly is close to your semitrailer, you should wheel it into position...?

Question 19 of 30

To check air flows to all trailers, you should let air pressure reach normal then...?

Question 20 of 30

On a triple combination, the shutoff valves at the rear off the middle trailer should be...?

Question 21 of 30

To check that the trailer emergency brakes are working properly, you should pull out the trailer air supply control and...?

Question 22 of 30

In this order, the shutoff valves at the rear of front trailers, the rear of the last trailer and the converter dolly air tank drain valve should be...?

Question 23 of 30

When connecting a converter dolly to a rear trailer, the trailer height must be adjusted so that it is...?

Question 24 of 30

Your tractor protection valve control should pop out, or go from normal to emergency position, when air pressure falls into what range?

Question 25 of 30

A bent or damaged kingpin on a coupling should be...?

Question 26 of 30

Before coupling a trailer, you should make sure it is at the right height using...?

Question 27 of 30

A dolly should be pulled out from a rear trailer using...?

Question 28 of 30

You can test that air is flowing to all trailers by opening...?

Question 29 of 30

When checking your air lines, they must be secure and...?

Question 30 of 30



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