Mississippi CDL: Double & Triple Trailers Practice Test

Not quite. The answer is Lower the second semitrailer's landing gear.

When uncoupling a set of standard doubles, the first unit to be uncoupled is the second semitrailer. To do this, lower its landing gear just enough to take some weight off the dolly. Then close the air shut-off valves on the first semitrailer and on the dolly (if so equipped). Disconnect the dolly's air and electrical lines from the second semitrailer. Release the dolly's fifth wheel latch, and pull the tractor forward so it pulls the dolly out from under the second semitrailer. After this is done, start to uncouple the dolly from the first semitrailer. These steps include lowering the dolly's landing gear and unhooking the dolly from the first semitrailer's pintle latch.

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 restore traction to the tires.

If braking or steering force exceeds the tires' traction with the road surface, a skid may result. You can recover from the skid by restoring sufficient traction.

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 You need about four times as much braking distance at 40 mph as at 20 mph.

Your total stopping distance is the sum of your perception distance (how far your vehicle goes from when you see the hazard until your brain processes it), reaction distance (how far the vehicle goes from when your brain orders your foot to take action until your foot actually starts to brake), and braking distance (how far the vehicle continues to travel once you apply the brake). Your vehicle's braking distance increases as the square of your speed. For example, you need about four times as much braking distance at 40 mph as you do at 20 mph.

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 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 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 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 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 Pull against the rear semitrailer's pin.

To check the coupling of the rear semitrailer, pull against the pin holding the rear semitrailer. Never move your vehicle until you are sure that all trailers are properly coupled.

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 rear trailer of a triple.

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 rearward amplification or the "crack-the-whip effect." For safety, position the heaviest trailer in front and the lightest trailer in the rear.

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 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 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 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 10

The formula for following distance is one second per ten feet of vehicle length, plus an extra second if you are traveling over 40 mph. Therefore, for a 100-foot vehicle traveling at 30 mph, you should leave a following distance of 100/10 = 10 seconds. (At or below 40 mph, you do not add an extra second.)

Not quite. The answer is 2

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 doubles described in your official state CDL handbook are connected with an A-dolly, which has a single drawbar connected to the front trailer. However, a B-double (also called a B-train double) has a two-drawbar B-dolly (or C-dolly), which is connected to two hitches in the front trailer. The two drawbar connections prevent this type of dolly from pivoting on the front trailer. The rear trailer connects to the dolly's fifth wheel. Hence, the only two pivot points are the tractor's fifth wheel and the B-dolly's fifth wheel. B-trains are legal in parts of Michigan and Washington State.

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.