Nevada CDL: Double & Triple Trailers Practice Test

Not quite. The answer is to lower its landing gear.

After you have uncoupled the rear trailer from the converter dolly, you need to uncouple the converter dolly from the front trailer. You do this as follows: 1. Lower the landing gear of the dolly. 2. Disconnect the safety chains. 3. Apply the dolly's spring brakes or chock its wheels to keep the dolly from moving. 4. Release the pintle hook connecting the dolly to the trailer ahead of it. 5. Slowly pull clear of the 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 drive through quickly.

If you drive through water at higher speeds, your tires may lose their grip of the road and start to skid. When driving through water, slow down and shift into a low gear. Increase engine rpm and apply the brakes gently to keep the brake linings pressed against the brake drums or discs. This will help keep contaminants out of the brakes.

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 closed.

To uncouple the second trailer, start by applying the parking brakes to keep your vehicle from moving. Lower the landing gear of the second trailer. Close the shut-off valves at the rear of the first trailer (and on the dolly if so equipped) to keep air from going out of the vehicle. Then disconnect the dolly air and electric lines, release the dolly brakes, and release the dolly fifth wheel latch. You are now ready to pull the first trailer and the dolly away from the second trailer.

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 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 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 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 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 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 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 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 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 use controlled or stab braking.

Hard braking and turning at the same time is likely to cause a skid. You should brake in a way that will keep your vehicle in a straight line and allow you to turn if necessary. If you need to brake suddenly to avoid a crash, use controlled braking or stab braking (but don't use stab braking if your vehicle has antilock brakes).

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 Older models may lack spring brakes.

All converter dollies built since 1975 are required to have spring brakes. All converter dollies built since 1998 are required to have antilock brakes as well.

Not quite. The answer is closed.

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 that the converter dolly air tank drain valve is closed.

Not quite. The answer is Allow much more space than is needed under ideal driving conditions.

The usual formula for following distance under ideal conditions is one second for every ten feet of vehicle length, plus an extra second if you are traveling at over 40 mph. The only thing the CDL manual says about following distance on slippery roads is that you should allow "much more space to stop." The Federal Motor Carrier Safety Administration (FMCSA) recommends doubling your usual following distance under poor driving conditions.

Source: "CMV Driving Tips - Following Too Closely," FMCSA, https://www.fmcsa.dot.gov/safety/driver-safety/cmv-driving-tips-following-too-closely

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.