Michigan CDL: Double & Triple Trailers Practice Test

Not quite. The answer is you couple the third trailer to the second trailer before you couple them to the first trailer.

A triple combination vehicle has four units (not counting the converter dollies): a tractor and three trailers. You couple a triple as follows: 1. Couple the first trailer to the tractor the same way that you couple any combination vehicle. 2. Couple the third trailer to the second trailer using the method for coupling doubles (which will involve the use of a converter dolly). 3. Move another converter dolly into position. 4. Couple the tractor and first trailer to the second and third trailer using the method for coupling doubles (which will involve another converter dolly).

Not quite. The answer is Brake and downshift in the curve.

Before entering a curve, slow down to a safe speed and downshift into the right gear. This lets you use some power through the curve to help keep the vehicle stable through the curve. It also allows you to speed up as soon as you are out of the curve.

Not quite. The answer is a yellow lamp on the left side.

A converter dolly with antilock brakes is required to have a yellow ABS lamp on its left side. All converter dollies built since March 1, 1998 have antilock brakes.

Not quite. The answer is Open at the rear of the front trailers and closed at the rear of the last trailer

Air must travel through the air lines of the tractor and all trailers – and that's all. Open the shut-off valves at the rear of each trailer but the last one to enable the air to flow to the trailer behind it. Close the shut-off valves at the rear of the last trailer to keep air from escaping.

Not quite. The answer is Either (a) or (b)

Federal regulation 49 CFR 380.205 states that you must meet various requirements before you can start training to operate a triple long combination vehicle. These requirements include 6 months' immediately prior experience driving either a tractor/semi-trailer combination or a tractor/semi-trailer/trailer combination, with a gross combination weight rating (GCWR) of at least 26,001 pounds.

Not quite. The answer is closed.

To uncouple the second trailer, start by applying the parking brakes to keep your vehicle from moving. Lower the landing gear of the second trailer. Close the shut-off valves at the rear of the first trailer (and on the dolly if so equipped) to keep air from going out of the vehicle. Then disconnect the dolly air and electric lines, release the dolly brakes, and release the dolly fifth wheel latch. You are now ready to pull the first trailer and the dolly away from the second trailer.

Not quite. The answer is the trailer will be raised slightly when the converter dolly is backed under it.

To connect the rear trailer to the converter dolly, the trailer must be at the right height. It should be slightly lower than the center of the dolly's fifth wheel so that the trailer will be raised slightly when the dolly is pushed underneath it.

Not quite. The answer is either of the above, if available.

You can secure the second trailer with either the spring brakes or the emergency air line. For an extra margin of safety, chock the wheels too.

Not quite. The answer is An additional drawbar

The type of converter dolly described in your official state CDL manual is an A-dolly. It has a single drawbar, whose eye fits over the pintle hook in the rear of a semitrailer. The A-dolly can pivot or articulate on that pintle hook. In contrast, a B-dolly (or C-dolly) has two drawbars, each with its own eye. These fit over two pintle hooks in the rear of a trailer. These two connections prevent the B-dolly from pivoting on the pintle hooks, thus eliminating one articulation or pivot point. B-dollies are used to connect B-doubles (also called B-train doubles).

Not quite. The answer is Use wheel chocks.

If the second trailer doesn’t have spring brakes, drive the tractor close to the trailer, connect the emergency line, charge the trailer air tank, and disconnect the emergency line. This will set the trailer emergency brakes (assuming the slack adjusters are correctly adjusted). However, if you have any doubt about the effectiveness of the trailer's braking system, chock the wheels.

Not quite. The answer is slow down.

You should always be able to stop within the distance you can see ahead. Your low-beam headlights let you see only about 250 feet ahead. At 55 mph, your vehicle will travel 250 feet in just 3.1 seconds – not enough time to notice and safely avoid a hazard that's within 250 feet of you. At 30 mph, your vehicle will travel 250 feet in 5.7 seconds.

Not quite. The answer is Use the engine brake or speed retarder.

A retarder supplements the braking force on the drive wheels. On a slippery surface, this may cause the wheels to lock, resulting in a skid. Turn off your retarder when driving on wet, icy, or snowy roads. Instead, slow down, increase your following distance, and try to brake gently.

Not quite. The answer is 20 to 45 psi.

The tractor protection valve keeps air in the tractor or truck brake system should the trailer break away or develop a bad leak. The tractor protection valve is designed to close automatically when the air pressure falls into the range specified by the manufacturer, typically 20–45 psi.

Not quite. The answer is the tractor protection valve control (trailer air supply control) will pop out or go from "normal" to "emergency."

When you test the tractor protection valve, the tractor protection valve control (also called the trailer air supply control) should pop out or go from the "normal" to the "emergency" position. This shows that the tractor protection valve has closed automatically to keep the air pressure from falling too far.

Not quite. The answer is open the shut-off valves at the rear of the first trailer and close the shut-off valves at the rear of the second trailer.

Air must travel through the air lines of the tractor and all trailers – and that's all. Open the shut-off valves at the rear of each trailer but the last one to enable the air to travel to the trailer behind it. Close the shut-off valves at the rear of the last trailer to keep air from escaping.

Not quite. The answer is Open the air tank petcock.

You release the dolly's brakes by opening the air tank petcock or (if the dolly is equipped with spring brakes) using the dolly's parking brake control.

Not quite. The answer is You should avoid traveling alongside other vehicles whenever possible.

Whenever another vehicle is traveling alongside yours, there's always a chance that the vehicle might try to move into your lane and accidentally hit your vehicle. Also, the vehicle is blocking you from changing lanes. It's safer to find an open spot where there are no vehicles on either side of you. (Of course, that may not be possible in heavy, congested traffic.)

Not quite. The answer is Older models may lack spring brakes.

All converter dollies built since 1975 are required to have spring brakes. All converter dollies built since 1998 are required to have antilock brakes as well.

Not quite. The answer is foot pedal.

The trailer hand valve (also called the Trolley Valve or Johnson Bar) operates only the trailer brakes, not the tractor brakes. Hence, use it only when you want to test the trailer brakes. Don't use it in normal driving because braking the trailers and not the tractor can cause a trailer to skid. The foot brake sends air to all the brakes on the vehicle – the tractor and all trailers. There is much less danger of causing a skid or jackknife when using just the foot brake.

Not quite. The answer is pull against the pin of the second trailer.

Test the coupling by pulling against the pin of the second semitrailer.