What endorsement is required to drive doubles and triples?

The T endorsement (Doubles/Triples) is required to legally operate doubles or triples combinations. It is obtained by passing the Doubles/Triples written knowledge test in addition to the general CDL written and skills tests. The endorsement does not require an additional skills test — the doubles handling characteristics are tested by the written exam and presumed to be similar to combination vehicle handling already tested for the basic CDL. The T endorsement is required for both standard doubles (28' + 28') and any LCV operation; LCV operation has additional state-level qualifications and training requirements on top of the T endorsement. There is no separate 'triples-only' endorsement; the T covers both.