New Jersey CDL: Double & Triple Trailers Practice Test

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 a coupling device that connects a semitrailer to the rear of a tractor-trailer.

The converter dolly connects a semitrailer to the rear of a tractor-trailer, forming a double or triple combination.

Not quite. The answer is do both of the above.

In bad weather or mountain driving or on slippery roads, use extreme caution. When you drive a double or triple, you're pulling a lot of dead axles with just a few drive axles. This increases the chance of loss of traction, causing a skid. Also, rearward amplification makes the rearmost trailer much more prone to rolling over. Drive slowly around curves and turns and avoid sudden moves.

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 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 Closed

A pre-trip inspection of a double or triple combination vehicle includes an inspection of each converter dolly. Among other things, check that the converter dolly air tank petcock is closed.

Not quite. The answer is apply light pressure on the brakes.

Avoid driving through deep puddles or flowing water if possible. If not, slow down and downshift into a low gear. Gently press on the brakes and maintain pressure for a short distance when you are out of the water. This will heat up the brakes and dry them out. (However, don't overdo it, or the brakes may overheat.) Then apply the brakes to make a test stop when it is safe to do so.

Not quite. The answer is more likely to turn over.

In a double or triple combination, each trailer is more likely to roll over than the one in front of it. The rear trailer of a triple is 3.5 times as likely to roll over as a five-axle tractor-trailer. This is known as the "crack-the-whip" effect, caused by rearward amplification. For safety, position the heaviest trailer in front and the lightest trailer in the rear.

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 a separate air tank.

Federal regulations require brakes on every wheel of a combination vehicle, including the wheels of the semitrailers and converter dollies. Like semitrailers, dollies have their own air brakes and their own air tanks.

Source: 49 CFR § 393.42

Not quite. The answer is Charge the trailer's air tank and then disconnect the emergency air line.

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 air line. This will set the trailer emergency brakes (assuming the slack adjusters are correctly adjusted). Chock the wheels if you have any doubt about the brakes.

Not quite. The answer is make things look smaller and farther away than they really are.

A convex mirror has a wider field of view than a flat mirror. However, objects viewed in a convex mirror look smaller and farther away. Remember this when you're trying to judge the distance of an object that you're viewing in a convex mirror.

Not quite. The answer is Both (a) and (b)

Take special care when pulling two or three trailers. In bad weather, under slippery conditions, and in mountain driving, you must be especially careful. There is a greater risk of skids and loss of traction. Also, doubles and triples need more space because they can’t be turned or stopped suddenly. Maintain a greater following distance. Make sure you have large enough gaps before entering or crossing traffic.

Not quite. The answer is fifth; one or two

A semitrailer can be connected to a converter dolly because, like the rear of a typical tractor, it has a fifth wheel and one or two axles.

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 Rocky Mountain double

A double pup trailer consists of two 28.5-foot trailers, known as "pup trailers." A double pup trailer is also known as an STAA trailer, named for the Surface Transportation Assistance Act (STAA). This standard-double configuration is the only type of double trailer that is allowed nationwide. A Rocky Mountain double trailer consists of a 40- to 53-foot trailer followed by a 28.5-foot pup trailer. Rocky Mountain doubles are allowed in certain Western states. A turnpike double trailer consists of two 48-foot trailers. Turnpike doubles can be found traveling on expressways in the Eastern states.

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 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 The heaviest trailer

The rearmost trailer is much more likely to roll over than the front trailer. Position the heaviest trailer directly behind the tractor and position the lightest trailer at the rear.

Not quite. The answer is may have poor traction due to bouncing and wheel lockup.

Trucks brake best when they are used as they were designed: to carry a properly balanced load. Empty trucks actually have longer stopping distances than loaded trucks because they have less traction.