California Doubles/Triples CDL Practice Test

This is a free 20-question practice test for the Doubles/Triples portion of the California 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 California Department 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 California.

Question 1 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 2 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 3 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 4 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 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

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 7 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 8 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 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 "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 11 of 20

When testing the brakes on a doubles rig:

Do all the standard checks plus verify air pressure builds at the rear trailer and that brakes apply at all wheels
Only test the tractor
Only test the lead trailer
Skip the test

Correct. Test the entire rig: build-up time, leakage, low-pressure warning, parking brake, and confirm rear-trailer brake function.

Question 12 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 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

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 15 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 16 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 17 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 18 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 19 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 20 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.

About the California 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 California Department 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 California CDL practice tests.