Alabama Doubles/Triples CDL Practice Test

This is a free 20-question practice test for the Doubles/Triples portion of the Alabama 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 Alabama Law Enforcement Agency Driver License Division 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 Alabama.

Question 1 of 20

In a multi-trailer combination, the most violent movement during evasive maneuvers happens at:

The tractor
The first trailer
The last trailer
The cab

Correct. Rearward amplification (crack-the-whip effect) is greatest at the rear-most trailer. The last trailer in a triple can be thrown sideways with much greater force than the tractor.

Question 2 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 3 of 20

When pulling a heavy lead trailer and a light second trailer, the rig:

Will be more stable than the reverse
Is more likely to roll the rear trailer
Is illegal
Drives the same as either order

Correct. Heaviest in front, lightest in rear. Heavy at the rear amplifies crack-the-whip and rollover risk.

Question 4 of 20

When you encounter a breakaway in your doubles (a trailer separates):

Maintain control of the tractor and lead trailer, brake gently to a controlled stop, set warning devices, and contact dispatch
Brake hard
Speed up
Swerve sharply

Correct. Maintain control of what remains, brake gently and progressively, secure the area with warning devices, contact dispatch.

Question 5 of 20

Inspecting safety chains on a converter dolly:

Verify they are correctly crossed and have no broken links, deformations, or wear
Skip the chains
Replace them daily
Verify color only

Correct. Safety chains should be intact, no broken links or excessive wear, and properly crossed under the pintle for support.

Question 6 of 20

An empty rear trailer on a multi-trailer rig:

Is more likely to roll over in evasive steering than a loaded one
Is always stable
Cannot roll over
Has no effect

Correct. Lighter trailer = more vulnerable to crack-the-whip and crosswinds. Empty rear trailers in multi-trailer rigs roll easily.

Question 7 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 8 of 20

Crosswinds may cause the rear trailer of a doubles to:

Sway dangerously, especially when empty
Brake automatically
Steer itself
Have no effect

Correct. Empty trailers act as sails. Strong crosswinds can sway or even tip an empty rear trailer. Reduce speed in high winds.

Question 9 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 10 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 11 of 20

When inspecting a doubles or triples rig, you should additionally check:

Each pintle hook, each set of safety chains, each converter dolly, each trailer's lights, brake chamber connections, glad-hands, and shut-off valves
Only the lead trailer
Only the tractor
Only the cargo

Correct. Every connection point and every trailer needs inspection — pintle hooks, chains, dollies, lights, brake lines, glad-hands, and air-supply valves.

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

A "set of doubles" typically refers to:

A tractor pulling two trailers
One tractor with one long trailer
Two tractors and a trailer
Two tractors and two trailers

Correct. A "set of doubles" is one tractor pulling two trailers (typically two pups, each about 28 feet long, in LTL operations).

Question 14 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 15 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 16 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 17 of 20

When you couple a converter dolly to a lead trailer, you should:

Close the lead trailer's shut-off valves only after the second trailer is fully connected and air flows
Open all valves at the start
Skip air supply
Close everything before connecting

Correct. Manage shut-off valves so air supply is restored to the rear trailer in proper sequence; verify with brake checks.

Question 18 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 19 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 20 of 20

Before connecting a converter dolly, you should:

Inspect tires, brakes, fifth-wheel jaws, and overall condition
Skip inspection
Only check the tires
Only check the lights

Correct. Pre-trip the dolly: tires, brake adjustment, fifth-wheel jaws (open and clean), pintle hook, electrical receptacle, lights.

About the Alabama 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 Alabama Law Enforcement Agency Driver License Division 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 Alabama CDL practice tests.