CDL test guide · 50 states
CDL Doubles and Triples Test Guide
Pulling two or three trailers, for endorsement T. Taken for Class A.
What every manual says
Handling and space with more than one trailer, coupling with a converter dolly, the walk-around and the extra air brake checks.
Pulling Double/Triple Trailers
Pulling two or three trailers needs special care: more things can go wrong, and doubles and triples are less stable than other commercial vehicles.
Prevent Trailer from Rolling Over
To keep trailers from rolling over, steer gently and go slowly around corners, ramps and curves; a curve speed safe for a straight truck or single-trailer combination may be too fast for doubles or triples.
Manage Space
Doubles and triples take up more space: they are longer and can't be turned or stopped suddenly, so allow more following distance.
Adverse Conditions
Be especially careful in bad weather, slippery conditions and mountains with doubles and triples: greater length and more dead axles pulled by your drive axles mean more chance of skids and loss of traction.
Parking the Vehicle
When parking doubles or triples, don’t get into a spot you can’t pull straight through; know how parking lots are laid out to avoid a long, difficult escape.
Coupling Twin Trailers
For the safest handling, the more heavily loaded semitrailer goes first, behind the tractor, and the lighter trailer in the rear.
Coupling and Uncoupling
A converter dolly is a coupling device with one or two axles and a fifth wheel, used to couple a semitrailer to the rear of a tractor-trailer to form a double.
Coupling and Uncoupling Triple Trailers
To take apart a triple, uncouple the third trailer first (pull the dolly out, then unhitch it as for doubles), then uncouple the rest as for any double.
Inspecting Doubles and Triples
On a doubles or triples walk-around, be sure the dolly's pintle-eye is in place in the trailer's pintle hook and the pintle hook is latched.
Additional Air Brake Checks
On doubles and triples, the extra air brake checks include the tractor protection valve: with the trailer air system charged and the engine off, pump the brake pedal to lower tank pressure.
Manage Space
With doubles and triples, make sure gaps are large enough before entering or crossing traffic, and be certain the sides are clear before changing lanes.
Coupling and Uncoupling
If it's close, wheel the converter dolly into position by hand, in line with the kingpin; otherwise pick it up with the tractor and first semitrailer: couple it to the rear of the first trailer, lock the pintle hook and raise the dolly support.
Coupling and Uncoupling Triple Trailers
Coupling methods differ for the many other truck-trailer and tractor-trailer combinations; learn the right way for your vehicle from the manufacturer's or owner's specifications.
Inspecting Doubles and Triples
Other doubles and triples walk-around checks: air lines supported and glad hands properly connected, any spare tire on the dolly secured, safety chains secured to the trailers, and light cords firmly in their sockets.
Additional Air Brake Checks
To test the trailer emergency brakes on doubles and triples: charge the trailer air system, check that the trailers roll freely, then pull out the trailer air supply control (or set it to emergency) and pull gently with the tractor to check that the emergency brakes are on.
Pulling Double/Triple Trailers
Doubles and triples have more critical parts to check than single-trailer rigs, so inspect all of them.
Every state's manual: Doubles and Triples
Each links its doubles and triples practice test. Federal CDL rules: endorsement T and the others.
- AlabamaSection 7 · p. 99–102
- AlaskaSection 7 · p. 102–105
- ArizonaSection 7 · p. 100–103
- ArkansasSection 7 · p. 96–99
- CaliforniaSection 7 · p. 133–138
- ColoradoSection 7 · p. 84–87
- ConnecticutSection 7 · p. 97–100
- DelawareSection 7 · p. 103–106
- FloridaSection 7 · p. 103–106
- GeorgiaSection 7 · p. 181–189
- HawaiiSection 7 · p. 105–108
- IdahoSection 7 · p. 96–99
- IllinoisSection 7 · p. 93–97
- IndianaSection 7 · p. 97–100
- IowaSection 7 · p. 101–104
- KansasSection 7 · p. 96–99
- KentuckySection 7 · p. 106–109
- LouisianaSection 7 · p. 117–120
- MaineSection 7 · p. 99–102
- MarylandSection 7 · p. 200–208
- MassachusettsSection 7 · p. 122–125
- MichiganSection 7 · p. 109–112
- MinnesotaSection 7 · p. 143–146
- MississippiSection 7 · p. 96–99
- MissouriSection 7 · p. 93–96
- MontanaSection 7 · p. 104–107
- NebraskaSection 7 · p. 108–111
- NevadaSection 7 · p. 104–107
- New HampshireSection 7 · p. 96–99
- New JerseySection 7 · p. 96–100
- New MexicoSection 7 · p. 99–102
- New YorkSection 7 · p. 116–123
- North CarolinaSection 7 · p. 99–102
- North DakotaSection 7 · p. 97–100
- OhioSection 7 · p. 91–94
- OklahomaSection 7 · p. 96–99
- OregonSection 7 · p. 99–102
- PennsylvaniaSection 7 · p. 124–128
- Rhode IslandSection 7 · p. 92–95
- South CarolinaSection 7 · p. 111–114
- South DakotaSection 7 · p. 119–122
- TennesseeSection 7 · p. 101–104
- TexasSection 7 · p. 105–108
- UtahSection 7 · p. 101–104
- VermontSection 7 · p. 109–112
- VirginiaSection 7 · p. 96–99
- WashingtonSection 7 · p. 103–106
- West VirginiaSection 7 · p. 134–137
- WisconsinSection 7 · p. 139–144
- WyomingSection 7 · p. 93–98