Doubles & triples endorsement (T)
T is the cheapest endorsement to add and the one with the widest gap between what it legally permits and what you will actually be allowed to pull. Most of the country does not allow triples at all.
- Code
- T
- Test
- Knowledge test only — no skills test
- Background check
- None
- Typical state fee
- Usually under $25
- Prerequisite
- Class A CDL
Ready to check yourself? Take the free Doubles/Triples (T) practice test — no sign-up.
What it actually lets you pull
The T endorsement covers pulling more than one trailer — a set of doubles, or triples where they are legal. It sits on top of a Class A CDL, because pulling any trailer combination over the weight thresholds already requires Class A.
The legal reality is narrower than the endorsement. Triples are permitted only in a minority of states, mostly in the west, and even there they are restricted to specific highways. Doubles are far more common and are what most LTL freight networks run.
What the knowledge test covers
The test is knowledge-only and it concentrates on the two things that make multiple trailers dangerous: coupling them in the right order and the way the rear trailer amplifies every steering input.
Crack-the-whip is the concept the test keeps returning to. The last trailer in a set travels faster sideways than the tractor does, which is why rollover risk climbs with each unit you add and why the heaviest trailer always goes first.
- Coupling and uncoupling order for doubles and triples
- Converter dollies, pintle hooks and safety chains
- Crack-the-whip and rearward amplification
- Which trailer goes where — heaviest first
- Air line routing and the shut-off valve checks
Is it worth adding?
For its cost, T is usually the highest-return endorsement on the list. It is a single written test with no background check, and it opens LTL and regional line-haul work where doubles are standard equipment.
It also pairs cleanly with other endorsements — a driver with T and N, or T and X, covers a noticeably wider slice of freight than a Class A alone.
Frequently asked
- Do I need a Class A CDL for the doubles/triples endorsement?
- In practice yes. Pulling multiple trailers puts you into combination-vehicle territory, which is Class A. The endorsement is added on top of that license.
- Is there a skills test for doubles and triples?
- No. T is a knowledge test only. You will not be asked to couple a set at the licensing office.
- Are triples legal everywhere?
- No. Only a minority of states allow triple trailers, generally in the west and generally restricted to designated highways. Doubles are permitted much more broadly.
- Which trailer goes first in a set of doubles?
- The heaviest one goes directly behind the tractor. Putting a light trailer first and a heavy one at the rear worsens rearward amplification and rollover risk — and it is a favourite test question.