Colorado Doubles/Triples CDL Practice Test

This is a free 20-question practice test for the Doubles/Triples portion of the Colorado 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 Colorado Division of Motor Vehicles 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 Colorado.

Question 1 of 20

When pulling triples, you should:

Make abrupt lane changes
Drive in the right lane and avoid abrupt steering
Drive in the left lane
Drive at top speed

Correct. Stay right, plan lane changes well in advance, signal early, and avoid abrupt steering. Triples crack-the-whip violently.

Question 2 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 3 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.

Question 4 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 5 of 20

When backing a doubles or triples combination:

Avoid it whenever possible — multi-trailer rigs cannot be backed any meaningful distance safely
Back at full speed
Back without a helper
Use only the trailer brake

Correct. Doubles and triples cannot be backed safely beyond a few feet — joints flex unpredictably. Plan your route and parking to avoid backing.

Question 6 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 7 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 8 of 20

During a pre-trip on doubles, the trailer-supply line:

Should be open from tractor to rear-most trailer
Should be open at the front but closed at the rear-most trailer
Should be closed everywhere
Should always be disconnected

Correct. The supply line carries air from tractor through every trailer; verify open valves at every coupled connection and a closed valve at the rear of the rear-most trailer.

Question 9 of 20

When inspecting a doubles rig, the lights on the rear of the rear-most trailer must:

Be visible, working, and not blocked by the lead trailer
Only the lead trailer's lights matter
Be off
Not be checked

Correct. Brake, turn, and marker lights at the rear of the rearmost trailer must be working and visible — that is what following traffic sees.

Question 10 of 20

A doubles rig is more likely to roll over than a single because:

The center of gravity is higher
The crack-the-whip effect amplifies steering input at the rear, where rollover threshold is lower
It is heavier
It is shorter

Correct. Multi-trailer rollover comes from rearward amplification — even modest steering input at the tractor becomes a violent swing at the rear trailer.

Question 11 of 20

A safe practice when starting from a stop with doubles:

Accelerate gently to avoid breakaway sway in the second trailer
Floor the accelerator
Use only the trailer hand valve
Skip first gear

Correct. Sudden acceleration can cause the rear trailer to sway. Start gently in low gear.

Question 12 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 13 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 14 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 15 of 20

On a triple, the air pressure to the rearmost trailer:

Is the same as the lead
Is delayed by line length, so braking response at the rear trailer lags noticeably
Is faster
Does not exist

Correct. Greater line length = greater brake-lag at the rear. Plan braking earlier than you would for a single trailer.

Question 16 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 17 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 18 of 20

When making a lane change in a doubles rig, you should:

Signal early, check mirrors, change lanes gradually
Snap the wheel
Use only the trailer hand valve
Skip the signal

Correct. Early signal, mirror check, gradual lane change. Quick lane changes amplify into the rear trailer.

Question 19 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 20 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.

About the Colorado 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 Colorado Division of Motor Vehicles 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 Colorado CDL practice tests.