North Dakota 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 B.

If you swing wide to the left before you turn right, another vehicle may try to pass you on your right while you are turning. Instead, as shown in path B, make the right turn with the rear of your vehicle as close to the curb as possible and turn wide as you complete the turn. This will deny other vehicles enough room on the right to try to pass you.

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 Go to the rear of the second trailer and open the emergency line shut-off valve.

To check whether air is being supplied to the second trailer, go to the rear of the trailer and open the emergency line shut-off valve. You should hear air escaping, indicating that the entire system is charged up to that point. (For a triple combination vehicle, perform this procedure with the third trailer.)

Not quite. The answer is sometimes lack antilock brakes.

All trailers and converter dollies built since March 1, 1998 are required to have antilock brakes (ABS).

Not quite. The answer is There are more critical parts to check.

There is nothing inherently wrong with double or triple trailers. There are just more critical parts to check. For a triple, you must check the critical parts of three trailers and two converter dollies, problems in any of which can cause serious trouble.

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 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 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 The rig may jackknife.

Check your mirrors to monitor your trailers and see if a trailer has begun to skid. Do this every time you have to brake hard. Once the wheels of a trailer begin to skid, the risk of jackknifing is high. Once the trailer swings out of your lane completely, you may not be able to prevent a jackknife.

Not quite. The answer is the shut-off valves, the converter dolly or dollies, and the air brakes on all trailers.

To inspect a double or triple, first inspect it just as you would inspect any combination vehicle. Then check that the shut-off valves are open on all trailers but the last trailer. Check each converter dolly to be sure that the pintle hook is properly latched.

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 less

Double and triple vehicles are more prone to rolling over or jackknifing than single vehicles are. Avoid 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 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 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 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.

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 The more sharply you turn, the greater the chances of a skid or rollover.

Don't turn any more than needed to clear whatever is in your way. The more sharply you turn, the greater the chances of a skid or rollover.

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 Allow a greater following distance than for smaller commercial vehicles.

Doubles and triples need more space because they can’t be turned or stopped suddenly. Allow a greater following distance behind the vehicle in front of you.