CDL Doubles & Triples Practice Test
The Doubles & Triples endorsement (T) authorizes you to pull double and triple trailer combinations. It's a favorite endorsement for LTL and package-delivery drivers because it opens up higher-paying line-haul jobs — but it also carries more risk than pulling a single trailer.
This free CDL Doubles & Triples practice test covers everything the written knowledge test asks about: how to couple and uncouple multi-trailer combinations in the correct order, how rearward amplification makes the rear trailer whip in emergency maneuvers, and how to inspect and maintain converter dollies.
What this test covers
- Coupling doubles and triples in the correct order (heaviest first)
- Converter dollies: parts, coupling, and inspection
- Rearward amplification and trailer whip
- Managing space, following distance, and rollover risk
- Inspecting doubles and triples
- Handling doubles and triples in wind and turns
How to study
- Remember: the heaviest trailer goes directly behind the tractor; lighter trailers go to the rear.
- Learn the crank direction on the dolly and how to check the safety chains and pintle hook.
- Rearward amplification means the last trailer can move 2–3 times more than the tractor — never make sudden lane changes.
Frequently asked questions
- Is the Doubles & Triples endorsement legal in every state?
- Doubles are legal in every U.S. state. Triples are restricted or banned in some states — check the state where you'll be driving before adding the T endorsement.
- How many questions are on the Doubles & Triples test?
- Most states give a 20-question T endorsement knowledge test and require 80% (16 out of 20) to pass.
- Do I need Combination Vehicles before Doubles & Triples?
- You need a Class A CDL, which means passing Combination Vehicles first. Doubles & Triples is added on top of the Class A credential.
Ready to start?
Practice this CDL topic free — no account needed for your first session. Unlock the full course when you're ready.