Doubles and Triples Practice Test
Required to tow two or three trailers. Coupling order, converter dollies, crack-the-whip, and why the lightest trailer goes last.
This is the T endorsement knowledge test. Passing it adds T to your commercial licence.
Do you need this test?
Optional — you only need it if you will actually be driving this way. Every CDL applicant takes the general knowledge test first.
Practice now
Study the material, not just the questions
Every input amplifies as you add trailers behind the tractor.
Open the Doubles & Triples moduleThe other tests you'll need
- General Knowledge — 50 questions · 80% to pass
- Air Brakes — 25 questions · 80% to pass
- Combination Vehicles — 20 questions · 80% to pass
- Hazardous Materials — 30 questions · 80% to pass
- Tank Vehicles — 20 questions · 80% to pass
- Passenger Transport — 20 questions · 80% to pass
- School Bus — 20 questions · 80% to pass
- LCV Doubles — 30 questions · 80% to pass
- LCV Triples — 30 questions · 80% to pass
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Sample Doubles and Triples questions
When driving doubles or triples, you should look farther ahead than usual because:
- A. You have better visibility
- B. You can drive faster
- C. Stopping distance is much longer
- D. The trailers are lighter
Show answer
C. Stopping distance is much longer — Doubles and triples need significantly more stopping distance. Look farther ahead to anticipate stops and slow-downs.
Universal rule · checked against FMCSA Commercial Driver License Manual — Section 7: Doubles and Triples · verified 2026-05-17
The converter dolly connects:
- A. The first trailer to the second trailer
- B. The tractor to the first trailer
- C. The steering axle to the drive axle
- D. Air lines between trailers
Show answer
A. The first trailer to the second trailer — The converter dolly couples the rear of the first trailer to the front of the second trailer in a doubles combination.
Universal rule · checked against FMCSA Commercial Driver License Manual — Section 7: Doubles and Triples · verified 2026-05-17
Rollovers of doubles/triples are most likely to happen when:
- A. Driving in a straight line
- B. During pre-trip inspection
- C. Backing up
- D. Making sudden lane changes or taking curves too fast
Show answer
D. Making sudden lane changes or taking curves too fast — Rearward amplification and high center of gravity make doubles/triples prone to rollover during sudden lane changes and curves taken too fast.
Universal rule · checked against FMCSA Commercial Driver License Manual — Section 7: Doubles and Triples · verified 2026-05-17
To prevent a loss-of-control situation with doubles/triples, you should:
- A. Keep speed well below the limit on curves and steer smoothly
- B. Accelerate hard on curves
- C. Drive the speed limit always
- D. Use the trailer hand brake in turns
Show answer
A. Keep speed well below the limit on curves and steer smoothly — Drive below the speed limit on curves, steer smoothly, avoid abrupt maneuvers, and maintain a greater following distance.
Universal rule · checked against FMCSA Commercial Driver License Manual — Section 7: Doubles and Triples · verified 2026-05-17
How should you check that the converter dolly fifth wheel is properly locked after coupling?
- A. Try to pull the combination apart by moving forward slowly and check for separation
- B. Check that the safety chains are hooked correctly
- C. Push and pull the converter dolly by hand
- D. Pull forward with full throttle to test tension on the connection
Show answer
A. Try to pull the combination apart by moving forward slowly and check for separation — After coupling, check the fifth wheel lock by slowly moving forward to put tension on the coupling, then stop and verify no separation occurred between the dolly and the trailer.
Universal rule · checked against FMCSA CDL Testing System — Doubles/Triples — Doubles and Triples — Coupling Check · verified 2026-06-30
Frequently asked questions
How many questions are on the Doubles and Triples test?
20 multiple-choice questions, and you need 80% correct — so you can miss 4. The federal standard is consistent across nearly every state.
Is this Doubles and Triples practice test free?
Yes. Every practice test here and everything in the DMV Prep app is free — no ads, no paywall, no account.
Where do these questions come from?
The FMCSA Commercial Driver's License Manual and 49 CFR. Every question carries its citation, which you can open from the answer explanation.
