Missouri CDL: Double & Triple Trailers Practice Test

Not quite. The answer is 5

In this context, articulation or pivoting means movement between two units separated by a joint, such as between a tractor and a trailer. A triple combination has 3 semitrailers connected with 2 converter dollies. This combination has 5 points of articulation: (1) the fifth wheel of the tractor; (2) the pintle hook of the first trailer; (3) the fifth wheel of the first converter dolly; (4) the pintle hook of the second trailer; and (5) the fifth wheel of the second converter dolly.

Not quite. The answer is only the more common types of combinations.

The official CDL manual's section on double and triple trailers usually describes how to couple and uncouple the more common types of double and triple combinations. However, there are other ways of coupling and uncoupling the many types of truck-trailer and tractor-trailer combinations that are in use. To learn how to couple and uncouple the vehicles you will be driving, consult the manufacturer's or owner's specifications.

Not quite. The answer is slightly raised.

To test the coupling of the dolly to the second trailer, you'll pull the tractor forward so the dolly will pull against the kingpin of the second trailer. Before doing so, raise the trailer's landing gear slightly. This will prevent damage if the trailer moves, and prevent the trailer from falling onto the ground if the dolly pulls away from the trailer.

Not quite. The answer is The dolly tow bar may fly up.

If you unlock the pintle hook while the dolly is still underneath the rear trailer, the dolly's tow bar may fly up, making it harder to recouple and possibly injuring someone.

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 park the vehicle in a straight line on firm level ground.

To uncouple the rear trailer, the first thing you do is park the vehicle in a straight line on firm level ground. Apply the parking brakes to keep the vehicle from moving. If the second trailer doesn't have spring brakes, chock its wheels.

Not quite. The answer is enough to remove some of the trailer's weight from the converter dolly.

Lower the landing gear of the second semitrailer enough to remove some of the trailer's weight from the converter dolly. This will make it easier to pull the dolly out from under the trailer.

Not quite. The answer is The pintle eye of the dolly should be in place in the pintle hook of the trailer.

A pre-trip inspection of a double or triple combination vehicle includes an inspection of each converter dolly in the vehicle. Among other things, check the coupling of the dolly to the trailer in front. Make sure that the pintle eye of the dolly is in place in the pintle hook of the trailer, and the pintle hook is latched closed.

Not quite. The answer is the vehicle is more likely to roll over or jackknife.

A double or triple combination vehicle is more likely to roll over or jackknife from sudden braking or steering changes. Look far enough ahead that you can slow down or change lanes gradually when necessary.

Not quite. The answer is You must drive a double or triple very smoothly to avoid a rollover or jackknife.

Take special care when pulling two or three trailers. Doubles and triples are more likely to turn over than other combination vehicles because of the "crack-the-whip" effect. You must steer gently when pulling trailers. To prevent the trailers from rolling over, you must steer gently and go slowly around corners, on-ramps, off-ramps, and curves.

Not quite. The answer is Neither of the above will cause it.

Despite what footnote 5 in 49 CFR 393.11 says, Operational Policy 15 of the North American Standard Out-of-Service Criteria states that a converter dolly must have one stop lamp, one tail lamp, and (if the dolly obscures the tractor's rear turn signals) turn signal lights, but only when the dolly is being towed singly and is not towing a trailer. In a full multi-trailer configuration, the rearmost trailer must have working stop lights and taillights, of course.

Not quite. The answer is How the rear wheels follow a different path from the front wheels in a turn

Off-tracking is defined as the different paths taken by the front and rear wheels in a turn. The longer the vehicle, the greater the difference will be. As a result, the path followed by a tractor will be wider than the path of the rig itself. To compensate, you must steer the tractor wider to keep the rig from overrunning the curb or hitting some object.

Not quite. The answer is leaks of air or hydraulic fluid

Check the landing gear as part of your walk-around inspection. Check that no parts are missing and it isn't bent or damaged. If the landing gear is power operated, check its hoses, fittings, and other parts for signs or sounds of escaping air or hydraulic fluid.

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 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 may be too fast for a set of doubles or triples.

On curves, doubles and triples are more likely to roll over than other combination vehicles. A safe speed on a curve for a straight truck or a single-trailer combination vehicle may be too fast for a set of doubles or triples. To prevent trailers from rolling over, you must steer gently and go slowly around corners, on-ramps, off-ramps, and curves.

Not quite. The answer is Overloaded front axles can make the steering axle weight too light to steer safely.

Underloaded front axles (caused by shifting weight too far to the rear) can make the steering axle weight too light to steer safely.

Not quite. The answer is supply air to the trailer air brake system with the tractor and then disconnect the emergency line.

If the second trailer lacks spring brakes, set the emergency brakes or chock the wheels.

Not quite. The answer is using the dolly's parking brake control.

To connect the converter dolly to the first semitrailer, release the dolly's brakes so it can be moved. You release the dolly's brakes by opening the air tank petcock (valve) or using the dolly's parking brake control if the dolly is equipped with spring brakes.

Not quite. The answer is enough to take some of the weight off the dolly.

When uncoupling a loaded second or third semitrailer, lower the landing gear until it makes firm contact with the ground. Then crank the landing gear in low gear for a few more turns – just enough to lift some weight off the dolly, but not so much that you lift the trailer off the fifth wheel. This will make it easier to unlatch the fifth wheel now and couple the trailer next time.