Maryland Doubles/Triples CDL Practice Test

This is a free 20-question practice test for the Doubles/Triples portion of the Maryland 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 Maryland Motor Vehicle Administration 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 Maryland.

Question 1 of 20

When uncoupling the converter dolly from the lead trailer:

Lower trailer landing gear (if applicable), disconnect air and electrical, remove safety chains, then release pintle hook
Just unhook the chains and pull away
Drive forward fast
Use only the trailer brake

Correct. Standard sequence: support the trailer (landing gear if it is a semi-trailer), disconnect lines, remove chains, release pintle hook.

Question 2 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 3 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 4 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 5 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 6 of 20

On a steep downgrade with doubles, you should:

Select a lower gear before starting down and use intermittent firm braking
Coast in neutral
Use only trailer brake
Stay in high gear

Correct. Same rule as any combination vehicle, but plan extra margin: doubles take longer to stop and the rear trailer may push.

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

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 9 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 10 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 11 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 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

When pulling doubles in a tunnel:

Stay alert; clearance and turning radius can be tight
Drive faster
Stop in the middle
Honk continuously

Correct. Tunnel clearance can be tight for long doubles — watch overhead and side clearance, and respect any vehicle-class restrictions.

Question 14 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 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

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 17 of 20

A driver licensed for Class A with all endorsements may drive any combination vehicle. The T endorsement allows:

Doubles and triples
Hazmat
Tanker
Buses

Correct. T endorsement specifically authorizes doubles and triples. Other endorsements (H, N, P, S) cover other categories.

Question 18 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 19 of 20

A "doubles" combination uses a tractor plus:

Two trailers connected by a dolly
One trailer
Three trailers
No trailers

Correct. Doubles = tractor + lead semi-trailer + converter dolly + second semi-trailer (which becomes a full trailer once on the dolly).

Question 20 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.

About the Maryland 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 Maryland Motor Vehicle Administration 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 Maryland CDL practice tests.