New! High Road 2.0! We have a new version of this program. You can find it here: High Road 2.0

Section 7: Double/Triple Trailer

7.1 Pulling Double/Triple Trailers

This section has information needed to pass the CDL knowledge exam for driving safely with double and triple trailers. (You also should study Sections 2, 5 and 6.)

Take special care when pulling two and three trailers. There are more things that can go wrong, and doubles/triples are less stable than other commercial vehicles. Some areas of concern are discussed below.

Prevent Trailers From Rolling Over

To prevent trailers from rolling over, you must steer gently and go slowly around corners, on ramps, off ramps and curves. 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.

Crack-the-Whip Effect

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. The last trailer in a combination is most likely to turn over. If you do not understand the crack-the-whip effect, study Section 6.1

Inspect Completely

There are more critical parts to check when you have two or three trailers. Check all of them by following the procedures described later in this section.

Look Far Ahead

Doubles and triples must be driven very smoothly to avoid rollover or jackknife. Therefore, look far ahead so you can slow down or change lanes gradually when necessary.

Manage Space

Doubles and triples take up more space than other commercial vehicles. They are not only longer, but also need more space because they cannot be turned or stopped suddenly. Allow more following distance. Make sure you have large enough gaps before entering or crossing traffic. Be sure you are clear at the sides before changing lanes.

Adverse Conditions

Be more careful in adverse conditions. In bad weather, slippery conditions and mountain driving, you must be especially careful if you drive double and triple bottoms. You will have greater length and more dead axles to pull with your drive axles than other drivers. There is more chance for skids and loss of traction.

Remember: Suggested speed limits are not designed for trucks, let alone trucks pulling 2 or more trailers.
The "crack-the-whip" effect causes a dangerous situation for the second and third trailer. The last trailer is especially at risk of rolling over due to this effect. Many double/triple trailers experience a rollover of the last trailer only.

CDL:

Commercial Driver's License (CDL)

A CDL is required to drive any of the following vehicles:

  • Any combination of vehicles with a gross combined weight rating (GCWR) of 26,001 or more pounds, providing the gross vehicle weight rating (GVWR) of the vehicle being towed is in excess of 10,000 pounds.
  • Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing another not in excess of 10,000 pounds.
  • Any vehicle, regardless of size, designed to transport 16 or more persons, including the driver.
  • Any vehicle required by federal regulations to be placarded while transporting hazardous materials.

Combination Vehicle:

A vehicle with two separate parts - the power unit (tractor) and the trailer. Tractor-trailers are considered combination vehicles.

Doubles:

Refers to pulling two trailers at the same time, otherwise known as "pups" or "pup trailers" because they're only about 28 feet long. However there are some states that allow doubles that are each 48 feet in length.

OWI:

Operating While Intoxicated

Review Questions - Click On The Picture To Begin...

Why do you need to manage your space better while pulling doubles/triples?
  • Doubles / triples tend to be blown around more during windy conditions
  • All of these answers are correct
  • Doubles / triples require more stopping distance to avoid a jackknife
  • Doubles / triples take up more space in turns

Quote From The CDL Manual:

Doubles and triples take up more space than other commercial vehicles. They are not only longer, but also need more space because they cannot be turned or stopped suddenly. Allow more following distance. Make sure you have large enough gaps before entering or crossing traffic. Be sure you are clear at the sides before changing lanes.

Next
Which of the following is true about pulling double or triple trailers?
  • Doubles/triples are less prone to rollovers than single trailer vehicles
  • Doubles/triples are easier to handle in windy conditions than single trailer vehicles
  • Doubles/triples are less stable than other commercial vehicles
  • Doubles/triples don't jackknife as easily as single trailer vehicles

Quote From The CDL Manual:

Take special care when pulling two and three trailers. There are more things that can go wrong, and doubles/triples are less stable than other commercial vehicles. Some areas of concern are discussed below.

TruckingTruth's Advice:

Pulling doubles or triples are much more dangerous in nearly every aspect of driving, which is why they require an additional endorsement. Be extra cautious when driving a truck with two or more trailers.

Prev
Next
How can you reduce your chances of a rollover accident when pulling two or three trailers?
  • When going around corners, you should make quick movements to swing the rear trailer around directly behind the tractor
  • Be mindful that 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.
  • Always put extra pressure on the service brake so that the rear trailer remains directly behind the first trailer
  • While taking a tight turn, be sure to brake during the entire turn

Quote From The CDL Manual:

Prevent Trailers From Rolling Over - To prevent trailers from rolling over, you must steer gently and go slowly around corners, on ramps, off ramps and curves. 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.

TruckingTruth's Advice:

When it comes to driving doubles or triples, everything you do should be slower and smoother than driving a vehicle with only one trailer.

Prev
Finish
Please select an option
[2,3,2]
3

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

Apply For Paid CDL Training Through TruckingTruth

Did you know you can fill out one quick form here on TruckingTruth and apply to several companies at once for paid CDL training? Seriously! The application only takes one minute. You will speak with recruiters today. There is no obligation whatsoever. Learn more and apply here:

Apply For Paid CDL Training

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