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Doubles and triples endorsement (T) practice test

25 free practice questions for this exam, each with the reason for the answer and where to look it up.

CDL endorsements: practice test

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CDL endorsements

Hazardous materials, tank vehicles, doubles and triples, passenger and school bus endorsement knowledge tests.

25 questions for this exam

About the exam

ExamDoubles and triples endorsement (T)
Who runs itState DMVs
WhereUnited States

Question count, time limit and pass mark differ by where you take it. Check the official candidate bulletin from the organisation that runs your exam.

Sample questions

Which combination has the greatest rearward amplification?

  1. A set of doubles
  2. A tractor-semitrailer
  3. A straight truck
  4. A set of triples
Show the answer

D. A set of triples

Rearward amplification grows with the number of trailers and articulation points, so triples have the most. A straight truck has none because it has no trailer.

Reference: AAMVA CDL Manual, Section 6.1 and 7.1

Compared with a five-axle tractor-semitrailer, a set of doubles needs:

  1. Less following distance because it has more brakes
  2. The same space, since the gross weight is similar
  3. More following distance and larger gaps in traffic
  4. More space only when the trailers are fully loaded
Show the answer

C. More following distance and larger gaps in traffic

Doubles and triples are longer and cannot be turned or stopped suddenly, so they need more room ahead and bigger gaps to enter or cross traffic. Extra axles do not make up for the extra length and instability.

Reference: AAMVA CDL Manual, Section 7.1

Why are doubles and triples more likely to skid or lose traction in bad weather?

  1. They have fewer brakes than a single trailer would have
  2. They carry less weight on each trailer axle
  3. They must run at lower tire pressures
  4. They have more length and more dead axles to pull
Show the answer

D. They have more length and more dead axles to pull

The drive axles must pull more length and more non-driven (dead) axles, so traction runs out sooner on slick roads. Every axle still has brakes.

Reference: AAMVA CDL Manual, Section 7.1

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