Tennessee Doubles/Triples CDL Practice Test

This is a free 20-question practice test for the Doubles/Triples portion of the Tennessee Commercial Driver's License knowledge exam. Questions are pulled from a pool of 50 drawn from the AAMVA CDL Manual, which is the source document the Tennessee Department of Safety and Homeland Security Driver Services uses to write its actual exam.

How it works: Click an answer. The correct choice highlights in green, and you'll see a short explanation. Aim for 85% or better before you sit for the real test in Tennessee.

Question 1 of 20

Drivers should always couple the heaviest trailer:

Behind the tractor (in the front position)
At the rear
In the middle
It does not matter

Correct. Heaviest trailer goes directly behind the tractor; lightest goes at the rear. This minimizes rearward amplification and rollover risk.

Question 2 of 20

A converter dolly is:

A small hand truck
A set of axles with a fifth wheel that converts a semi-trailer into a full trailer for use in doubles/triples
A trailer-loading device
A type of brake

Correct. A converter dolly has a small frame, axle(s), and a fifth wheel mounted on top — it transforms a semi-trailer into a full trailer behind another trailer.

Question 3 of 20

Driving doubles or triples on the highway:

Requires gentler steering, longer following distance, and earlier braking
Allows the same maneuvers as a single trailer
Allows higher cornering speeds
Has no special concerns

Correct. Multi-trailer rigs are more sensitive to abrupt steering, take longer to brake, and amplify any movement to the rear. Be gentle and plan ahead.

Question 4 of 20

A tractor pulling doubles cannot brake as quickly as a tractor pulling a single trailer because:

Doubles are heavier and brake response is delayed in longer air lines
Doubles are lighter
Brakes are bigger
Tractors brake better with doubles

Correct. Greater weight and longer air lines mean longer braking distance. Plan stopping distance with extra margin.

Question 5 of 20

You discover a flat tire on the rear trailer of a triple. You should:

Continue driving
Pull off safely, set warning devices, and have the tire repaired or replaced before continuing
Drive only at night
Drive faster to balance

Correct. A flat tire affects rig stability and brake load. Pull off safely, use warning devices, and address the tire.

Question 6 of 20

When parking a doubles rig:

Park where you can pull straight out — back-out is impractical
Back into any spot
Park in the entrance
Block the lane

Correct. Choose pull-through parking. Multi-trailer rigs cannot back any meaningful distance safely.

Question 7 of 20

The "T" endorsement is required to:

Drive any commercial vehicle
Pull two or more trailers
Drive a bus
Haul hazmat

Correct. The T endorsement is required to pull more than one trailer (doubles or triples).

Question 8 of 20

When coupling the second trailer to the converter dolly:

Position the dolly in front of the second trailer, lower trailer landing gear if necessary, lock the dolly to the lead trailer's pintle hook with safety chains, then back the second trailer onto the fifth wheel
Just push them together
Use the trailer hand valve
Drive past it fast

Correct. Position dolly, secure to lead-trailer pintle, then back second trailer over the fifth wheel and lock as a normal coupling.

Question 9 of 20

Glad-hand shut-off valves at the rear of trailers (for connecting to a following trailer) must be:

Open at the rear of the rear-most trailer
Open at the rear of any trailer that has another trailer behind it; closed at the rear of the last trailer
Always closed
Always open

Correct. Open the shut-off valves where the next trailer is connected; close them at the rear of the last trailer to prevent air loss.

Question 10 of 20

Safety chains on a converter dolly are required to:

Prevent the dolly from disconnecting if the pintle hook fails
Decorate the rig
Bind cargo
Add weight

Correct. Safety chains catch the dolly if the pintle hook releases or fails — preventing the trailer behind from breaking loose.

Question 11 of 20

Doubles and triples should not be driven:

On slippery roads at normal speed
On dry, straight highways
In any conditions
Only at low speed

Correct. On slippery roads, multi-trailer rigs lose stability quickly. Reduce speed substantially and increase following distance.

Question 12 of 20

Crosswinds are particularly hazardous for:

Empty doubles and triples
Loaded singles
Backing
Slow speeds

Correct. Empty trailers in a multi-trailer rig present a large flat surface to crosswinds — a strong gust can blow the rear trailer over.

Question 13 of 20

Air pressure on a triple-trailer rig takes:

Less time to reach the rear trailer than on a single
Significantly more time to reach the rear trailer's brake chambers
The same time
No air pressure is needed

Correct. Each additional trailer adds line length. Brake response at the rear trailer of a triple is noticeably delayed — brake earlier.

Question 14 of 20

A "drive-axle skid" on a doubles rig:

Can lead to a tractor jackknife and complicated trailer movement behind it
Is harmless
Means the dolly broke
Increases stability

Correct. A drive-axle skid leads to tractor jackknife. With trailers behind, the situation gets worse fast — the rear trailers can swing wildly.

Question 15 of 20

A "set of triples" typically refers to:

One tractor pulling three trailers
Three trailers without a tractor
Three tractors and one trailer
Three tractors only

Correct. A set of triples is one tractor pulling three trailers — usually allowed only on specific designated routes.

Question 16 of 20

When you uncouple a converter dolly, you should:

Disconnect air and electrical, secure or remove safety chains, then release the pintle hook
Just yank it off
Drive forward fast
Use only the trailer brake

Correct. Park level, disconnect air and electric, lower trailer landing gear if applicable, remove safety chains, then release the pintle hook to free the dolly.

Question 17 of 20

When pulling a single trailer and trying to figure out if you should add a doubles endorsement:

You only need T if you actually pull more than one trailer
T is required for any commercial driving
T is required only for tankers
T is required for any class A driver

Correct. The T endorsement is required only when you actually operate doubles or triples. Single-trailer operations do not require it.

Question 18 of 20

The driver of a doubles rig should:

Make slow, gradual steering and braking inputs
Drive aggressively
Use only the trailer brake
Honk frequently

Correct. Smooth, gradual inputs are critical. Avoid abrupt steering and abrupt braking.

Question 19 of 20

A pintle hook is:

The hitch on the rear of a trailer used to tow another trailer or dolly
The kingpin
The fifth wheel
A type of placard

Correct. The pintle hook is the strong rear-mounted hitch that grips the dolly's lunette eye, allowing one trailer to tow another behind it.

Question 20 of 20

Triples are restricted in many states. You should:

Drive triples anywhere
Verify state-by-state legality before crossing into a state
Use a special placard
Avoid driving in cities

Correct. Many states restrict triples to specific routes (turnpikes, designated corridors). Verify legality and route before crossing into a state.

About the Tennessee Doubles/Triples exam

Most states administer 20 Doubles/Triples questions and require 80% to pass. The exam emphasizes coupling and uncoupling the converter dolly, rearward amplification (the "crack-the-whip" effect), and the unique inspection and handling demands of multi-trailer rigs.

The Tennessee Department of Safety and Homeland Security Driver Services follows the federal CDL standards established by FMCSA. To earn the Doubles/Triples credential, you must answer at least 80% of the questions correctly. Many candidates score lower the first time because the test pulls from a large pool — refreshing this page will give you a different mix of questions, drawn from the same authoritative source.

Want more practice? Try the full Doubles/Triples question bank or browse all Tennessee CDL practice tests.