Arizona CDL: Double & Triple Trailers Practice Test

Not quite. The answer is Check your mirrors to keep an eye on your tires.

Use the mirrors to keep an eye on your tires. It's one way to spot a tire fire. But your mirrors don't eliminate all blind spots. Your truck still has large blind spots, often called No-Zones.

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 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.

Not quite. The answer is foot pedal.

You can use the trailer hand valve (also known as a spike or Johnson bar) to test the trailer service brakes. During normal driving, however, all the service brakes on your vehicle are controlled with the foot pedal, which applies air to the service brakes at all the wheels.

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.

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 air escape from the open valve.

Test the trailer brakes by opening the service line valve at the rear of the rig. You should hear the telltale hiss of air escaping. If you don't, it means that air is not flowing through the entire line, and you will need to investigate.

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 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 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 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 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 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 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 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 3

In this context, articulation or pivoting means movement between two units separated by a joint, such as between a tractor and a trailer. The standard or STAA double combination in the CDL handbook has 3 points of articulation: (1) the fifth wheel of the tractor; (2) the pintle hook of the front trailer; (3) the fifth wheel of the converter dolly.

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 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 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 Some do; some don't.

All converter dollies built since 1975 are required to have spring brakes. Older converter dollies that don't have spring brakes have emergency air brakes, which work from the air stored in the trailer air tank.