New Jersey Doubles/Triples CDL Practice Test

This is a free 20-question practice test for the Doubles/Triples portion of the New Jersey 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 New Jersey Motor Vehicle Commission 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 New Jersey.

Question 1 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 2 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 3 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 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

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.

Question 6 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 7 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 8 of 20

A converter-dolly fifth wheel must be:

Properly lubricated and have correctly functioning locking jaws
Painted
Wide
Empty

Correct. Inspect for proper lubrication, no excessive wear, and confirm the locking jaws operate correctly. The dolly fifth wheel is just as critical as the tractor's.

Question 9 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 10 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 11 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 12 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 13 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 14 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 15 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 16 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 17 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 18 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 19 of 20

When traveling on bridges with weight or length limits:

Verify the rig's overall length and weight comply with posted limits
Ignore signs
Drive faster
Honk the horn

Correct. Multi-trailer rigs may exceed length or weight limits on certain bridges. Plan routes to comply with posted limits.

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 New Jersey 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 New Jersey Motor Vehicle Commission 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 New Jersey CDL practice tests.