Michigan CDL: Combination Vehicles Practice Test

Not quite. The answer is Normal

To test the trailer air brake system, first charge it with air. Push in the red trailer air supply knob, or place the tractor protection valve control in the "normal" position. Wait until the air pressure reaches normal before you start your tests.

Not quite. The answer is Look under the vehicle for the ECU and wheel speed sensor wires coming from the back of the brakes.

You can tell if your vehicle has ABS by looking under the vehicle for the electronic control unit (ECU) and wheel speed sensor wires leading from the back of the brakes.

Not quite. The answer is Nothing is likely to happen until you try to apply the brakes.

If a leak has developed in the service line, air tank pressure may remain close to normal – until you try to brake. Then the air loss from the leak will cause the air pressure to drop quickly. If the air pressure drops far enough, the emergency brakes will come on.

Not quite. The answer is Never

The trailer hand valve (also known as a trolley valve or Johnson bar) controls only the trailer brakes, not the tractor brakes. You can use it to test the trailer brakes. But don't use it as a parking brake, especially if the trailer lacks spring brakes. If a leak causes loss of air pressure, the trailer brakes will fail. Don't use the trailer hand valve while you're driving either. Braking the trailer and not the tractor can cause the trailer to skid.

Not quite. The answer is the trailer's emergency brakes to come on.

The trailer air supply valve (which is manually controlled by the red dashboard knob) senses air pressure in the supply (emergency) line. If air pressure in the supply line is lost, the trailer air supply valve will close automatically, and the resulting loss of air pressure in the tractor protection valve will cause it to close as well. And loss of pressure in the supply line will cause the trailer emergency (spring) brakes to come on.

Not quite. The answer is always use the lowest reverse gear.

When coupling, use the lowest reverse gear and back slowly to avoid hitting or damaging the kingpin.

Not quite. The answer is Gently pull forward in low gear against the locked trailer brakes; then look at it carefully.

After you've backed under the trailer and locked the kingpin into the fifth wheel, raise the landing gear slightly. Then with the trailer brakes still locked, gently pull the tractor forward to check that the trailer is locked onto the tractor.

Not quite. The answer is tilted down toward the rear of the tractor.

Before coupling, make sure that the fifth wheel is in the proper position. For one thing, it should be tilted down toward the rear of the tractor so that the trailer can easily slide into it.

Not quite. The answer is two red lights

According to federal regulations, if the load projects more than 4 feet behind the rear of the vehicle, the end of the load must be marked as follows: (1) with two red flags, each 18 inches square, in the daytime; or (2) with two red lights at night. There are additional federal requirements on how to illuminate the rest of the load. US states may impose their own additional requirements on the transportation of oversized loads. You can learn about Michigan's requirements by contacting the Michigan Department of Transportation or visiting their webpage "MiTRIP – Overweight or Oversize Permits" (https://www.michigan.gov/mdot/0,1607,7-151-9625_56949-253714—,00.html). [49 CFR 393.11],

Source: 49 CFR 393.87

Not quite. The answer is 90 degrees

When connecting the glad hands, press the two seals together with the couplers at a 90-degree angle to each other. A turn of the glad hand attached to the hose will join and lock the couplers.

Not quite. The answer is to test the trailer brakes.

The trailer hand valve (also known as a trolley valve or Johnson bar) controls only the trailer brakes, not the tractor brakes. You can use it to test the trailer brakes. Don't use it while you're driving, though. If you apply it while you're driving, you'll brake the trailers but not the tractor, which can cause a skid. Instead, use the foot brake, which sends air to the tractor brakes as well as the trailer brakes.

Not quite. The answer is Control line and signal line

The service air line is also known as the control line or signal line.

Not quite. The answer is Apply and release the trailer service brakes while you listen for sounds.

If you cross the air lines, supply air will be sent to the service line instead of the supply line and the trailer air tanks. Without a supply of air, the trailer service brakes won't work. Therefore, to make sure that the air lines aren't crossed, send air to the trailer brakes by pushing in the trailer air supply control (red knob). Let the pressure normalize. Then turn off the engine and try the trailer brakes. You should see and hear the brakes in action and then see the air pressure normalize again.

Not quite. The answer is a Class A CDL with a Doubles/Triples (T) endorsement.

To legally pull a trailer whose gross vehicle weight rating (GVWR) exceeds 10,000 pounds, you'll have to obtain a Class A CDL. To pull triples, you'll also have to obtain a doubles/triples (T) endorsement on your CDL. Note: If you don't also pass a knowledge test on air brakes, your Michigan CDL will include restriction L, limiting you to driving only vehicles without air brakes.

Not quite. The answer is Fully raised with the crank handle secured in its bracket

Once you've coupled, raise the landing gear all the way up. If it's only partially raised, it could catch on something, such as the railroad tracks on a raised railroad crossing.

Not quite. The answer is If you make a quick lane change or sudden movement of your steering wheel, your trailers will tend to swing out. The rearmost trailer will swing out the most and will be most likely to roll over.

A sudden maneuver by the tractor may cause the rearmost (last) trailer to swing violently and possibly roll over. This is known as the crack-the-whip effect. It is caused by rearward amplification: The farther a trailer is from the tractor, the more likely it is to start swinging dangerously out of control.

Not quite. The answer is slightly raised.

After you've backed under the trailer and locked the kingpin into the fifth wheel, raise the landing gear slightly. Then with the trailer brakes still locked, gently pull the tractor forward to check that the trailer is locked onto the tractor.

Not quite. The answer is It should not be done.

The trailer hand valve (also known as a spike, a trolley valve, or a Johnson bar) controls only the trailer brakes, not the tractor brakes. If you apply it while you're driving, you'll brake the trailers but not the tractor. This can cause a trailer skid.

Not quite. The answer is a fully loaded trailer

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. The stiff suspension springs and strong brakes give poor traction and make it easier to lock the wheels.

Not quite. The answer is empty.

The weight of a full load adds traction. An empty or lightly loaded trailer is more likely to jackknife than a fully loaded one.