Washington CDL: Double & Triple Trailers Practice Test

Not quite. The answer is Never

Older vehicles may be equipped with manual front-wheel limiting valves. A control in the cab allows the driver to cut air pressure to the front brakes in half. It was thought that doing this would help reduce front-wheel skids on slippery roads. According to the CDL manual, however, more recent tests have shown that front-wheel braking is safe even on icy roads. Federal regulations now prohibit manual front-wheel limiting valves in vehicles manufactured since March 1, 1975. Automatic ratio valves, which limit front-axle braking only when brake applications are approximately 60 psi or less, are still permitted. These valves cannot be controlled manually by the driver. Note: The advent of antilock brakes (ABS) may make automatic ratio valves less useful as well.

Source: 49 CFR § 393.48

Not quite. The answer is latched.

When coupling a converter dolly to the trailer in front of it, place the dolly's pintle eye on the trailer's pintle hook. Latch the pintle hook closed. Secure the dolly's safety chains to the trailer.

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 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 A truck has less traction when it's empty than when it's fully loaded.

Trucks that are empty or only lightly loaded take longer to stop because the stiff suspension springs and strong brakes give poor traction and make it easier to lock the wheels.

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 A sudden movement with the steering wheel can result in a tipped-over rear trailer.

Because of rearward amplification (the "crack-the-whip" effect), the rearmost trailer is much more prone to rolling over. Avoid sudden steering changes that could cause the rearmost trailer to roll over.

Not quite. The answer is both of the above are true.

Check each landing gear to be sure that it is fully raised. Also check that no parts are missing and it isn't bent or damaged.

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.

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 closed; latched

When you do a walk-around inspection, you must ensure that the converter dolly is properly connected to the front trailer. Check that the pintle hook of the front trailer is locked onto the eye hook of the converter dolly and properly latched. Otherwise, the dolly could come loose. Even worse, if the dolly comes loose while it's still coupled to the rear trailer, the tow bar could fly up, possibly injuring someone.

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 Use your mirrors to keep an eye on your tires.

Clean and adjust your mirrors as part of your pre-trip inspection, when your vehicle is parked. Adjust each mirror to show some part of your vehicle as well as the roadway. You can adjust your mirrors accurately only when your trailers are straight. While you're driving, use your mirrors to keep an eye on your tires. It's one way to spot a tire fire. However, no matter how carefully you adjust your mirrors, there will still be blind spots that your mirrors cannot show you.

Not quite. The answer is open; closed

When you are inspecting a double or triple combination, make sure that the service and emergency line shut-off valves are open at the rear of each trailer except the last trailer, where they must be closed.

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 March 1998.

Antilock brakes have been required on all tractors built since March 1, 1997. Antilock brakes have been required on all trailers, converter dollies, buses, and single trucks built since March 1, 1998.

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.

When connecting the rear trailer to the converter dolly, lock the trailer brakes and raise the trailer landing gear slightly off the ground so it won't be damaged if the trailer moves. Then pull forward with the trailer brakes still locked, to check that the rear trailer is locked onto the converter dolly. If it's not, at least the landing gear will keep the rear trailer from falling onto the ground.

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 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.