TruckingTruth logo

Combination Vehicles Free CDL Practice Tests
Page 2

Prepare For The Combination Vehicles Portion Of Your CDL Written Exams

Combination Vehicles Questions

Click On The Picture To Begin

Good Luck!

Driving with an empty trailer:
  • Is safer when braking
  • Should never be attempted
  • Makes it harder to stop
  • Makes it easier to stop
Click here to look up the answer

From The CDL Manual

Brake Early —

Control your speed whether fully loaded or empty. Large combination vehicles take longer to stop when they are empty than when they are fully loaded. When lightly loaded, the very stiff suspension springs and strong brakes give poor traction and make it very easy to lock up the wheels. Your trailer can swing out and strike other vehicles. Your tractor can jackknife very quickly (see Figure 6-2 below). You also must be very careful about driving “bobtail” tractors (tractors without semitrailers). Tests show that bobtails can be very hard to stop smoothly. It takes them longer to stop than a tractor-semitrailer loaded to maximum gross weight.

Next
If the wheels of the trailer lock up and the trailer swings around, it could cause a:
  • Lawn job
  • Trailer jackknife
  • Bald tire
  • Traffic jam
Click here to look up the answer

From The CDL Manual

Prevent Trailer Skids —

When the wheels of a trailer lock up, the trailer will tend to swing around. This is more likely to happen when the trailer is empty or lightly loaded. This type of jackknife is often called a “trailer jackknife”

Prev
Next
The best and earliest way to recognize that your trailer has started to skid is:
  • Hearing loud noises
  • Smelling smoke
  • Other drivers pointing and waving
  • Looking in the mirrors
Click here to look up the answer

From The CDL Manual

Recognize the skid.

The earliest and best way to recognize that the trailer has started to skid is by seeing it in your mirrors. Any time you apply the brakes hard, check the mirrors to make sure the trailer is staying where it should be. Once the trailer swings out of your lane, it is very difficult to prevent a jackknife.

Prev
Next
When you notice that your trailer has lost traction and is going into a skid, you should:
  • Sound your air horn until you regain traction
  • Immediately slam on the brakes
  • Stop using the brake
  • Apply the trailer brakes
Click here to look up the answer

From The CDL Manual

Stop using the brake.

Release the brakes to get traction back. Do not use the trailer hand brake (if you have one) to “straighten out the rig.” This is the wrong thing to do because the brakes on the trailer wheels caused the skid in the first place. Once the trailer wheels grip the road again, the trailer will start to follow the tractor and straighten out.

Prev
Next
If your trailer goes into a skid, you should do all of the following except:
  • Keep the wheel straight
  • Use the trailer hand brake
  • Watch your mirrors
  • Release the brakes
Click here to look up the answer

From The CDL Manual

Following is the procedure for stopping a trailer skid:

1. Recognize the skid. The earliest and best way to recognize that the trailer has started to skid is by seeing it in your mirrors. Any time you apply the brakes hard, check the mirrors to make sure the trailer is staying where it should be. Once the trailer swings out of your lane, it is very difficult to prevent a jackknife.

2. Stop using the brake. Release the brakes to get traction back. Do not use the trailer hand brake (if you have one) to “straighten out the rig.” This is the wrong thing to do because the brakes on the trailer wheels caused the skid in the first place. Once the trailer wheels grip the road again, the trailer will start to follow the tractor and straighten out.

Prev
Next
When a vehicle goes around a corner, the rear wheels follow a different path than the front. This is called:
  • Side-tracking
  • Dog-pedalling
  • Off-tracking
  • Lolly-gagging
Click here to look up the answer

From The CDL Manual

Turn Wide —

When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels. This is called “offtracking” or “cheating.” Figure 6-4 on page 72 shows how offtracking causes the path followed by a tractor-semi to be wider than the rig itself. Longer vehicles will offtrack more. The rear wheels of the powered unit (truck or tractor) will offtrack some, and the rear wheels of the trailer will offtrack even more.

Prev
Next
To stop other drivers from passing you on the right when turning wide:
  • Go as slow as possible
  • Swerve back and forth
  • Keep the rear of your vehicle close to the curb
  • Wave them ahead on your left
Click here to look up the answer

From The CDL Manual

Steer the front end wide enough around a corner so the rear end does not run over the curb, pedestrians, other vehicles, etc. However, keep the rear of your vehicle close to the curb. This will stop other drivers from passing you on the right.

Prev
Next
If you have to enter another traffic lane to complete a wide turn, you should:
  • Turn wide as you complete the turn, instead of before it
  • Try to find a police officer to direct traffic
  • Stop and sound the air horn to make sure other vehicles get out of the way
  • Swing wide to the left before the turn
Click here to look up the answer

From The CDL Manual

Turn Wide —

If you cannot complete your turn without entering another traffic lane, turn wide as you complete the turn (see Figure 6-5 on page 72). This is better than swinging wide to the left before starting the turn because it will keep other drivers from passing you on the right. If drivers pass on the right, you may collide with them when you turn.

Prev
Next
While driving, you should use the trailer hand valve when?
  • Only in emergency
  • Traveling under 30 mph
  • Never use it while driving
  • When the trailer starts to skid
Click here to look up the answer

From The CDL Manual

Trailer Hand Valve —

The trailer hand valve (also called the “trolley valve” or “Johnson bar”) works the trailer brakes. The trailer hand valve should be used only to test the trailer brakes. Do not use it in driving because of the danger of making the trailer skid. The foot brake sends air to all the brakes on the vehicle (including the trailer(s’). There is much less danger of causing a skid or jackknife when using just the foot brake.

Prev
Next
The trailer hand valve should be used:
  • When the vehicle starts to skid
  • Along with the foot brakes
  • When parking
  • Only to test the trailer brakes
Click here to look up the answer

From The CDL Manual

Trailer Hand Valve —

The trailer hand valve (also called the “trolley valve” or “Johnson bar”) works the trailer brakes. The trailer hand valve should be used only to test the trailer brakes. Do not use it in driving because of the danger of making the trailer skid. The foot brake sends air to all the brakes on the vehicle (including the trailer(s’). There is much less danger of causing a skid or jackknife when using just the foot brake.

Never use the hand valve for parking because all the air might leak out, unlocking the brakes (in trailers that do not have spring brakes.) Always use the parking brakes when parking. If the trailer does not have spring brakes, use wheel chocks to keep the trailer from moving.

Prev
Finish
Please select an option
[3,2,4,3,2,3,3,1,3,4]
10

Join Us!

We have an awesome set of tools that will help you understand the trucking industry and prepare for a great start to your trucking career. Not only that, but everything we offer here at TruckingTruth is 100% free - no strings attached! Sign up now and get instant access to our member's section:
High Road Training Program Logo
  • The High Road Training Program
  • The High Road Article Series
  • The Friendliest Trucker's Forum Ever!
  • Email Updates When New Articles Are Posted

About Us

TruckingTruth was founded by Brett Aquila (that's me!), a 15 year truck driving veteran, in January 2007. After 15 years on the road I wanted to help people understand the trucking industry and everything that came with the career and lifestyle of an over the road trucker. We'll help you make the right choices and prepare for a great start to your trucking career.

Read More

Becoming A Truck Driver

Becoming A Truck Driver is a dream we've all pondered at some point in our lives. We've all wondered if the adventure and challenges of life on the open road would suit us better than the ordinary day to day lives we've always known. At TruckingTruth we'll help you decide if trucking is right for you and help you get your career off to a great start.

Learn More