Doubles & Triples CDL Practice Test

When pulling doubles or triples, the heaviest trailer should be:

• A. Behind the tractor (lead)
• B. In the rear
• C. In the middle
• D. Either

Why are doubles and triples more affected by wind?

• A. Multiple high boxes catch crosswinds; rearward amplification
• B. Lighter weight only
• C. Different tires
• D. Bigger engines

When you make a quick lane change in doubles, the rear trailer:

• A. Sways more (rearward amplification — possible rollover)
• B. Stays still
• C. Sways less
• D. Steers itself

What is a "converter dolly"?

• A. Coupling device with axle and fifth wheel that connects two trailers
• B. Spare tire
• C. Maintenance tool
• D. Loading ramp

When coupling a converter dolly to the second trailer, you must:

• A. Lock the kingpin in the dolly fifth wheel and connect safety chains
• B. Skip safety chains
• C. Use one chain only
• D. Skip locking

Doubles and triples have how many pivot points?

• A. Multiple — each coupling adds a pivot
• B. One
• C. Two only
• D. None

When inspecting doubles/triples, additional items include:

• A. All converter dollies, pintle hooks, safety chains, glad hands
• B. Tires only
• C. Fuel only
• D. Driver seat

Which trailer should you couple first?

• A. Lead trailer to tractor, then dolly to lead, then last trailer
• B. Last trailer first
• C. All at once
• D. Any order

What is "rearward amplification"?

• A. Sway intensifies as it travels through trailers — rear sways most
• B. Sound effect
• C. Engine vibration
• D. Brake noise

Why must you avoid sudden lane changes in triples?

• A. Rear can roll over due to amplified sway
• B. Wastes fuel
• C. Damages tires
• D. Slows traffic

When uncoupling a converter dolly, you must:

• A. Lower trailer landing gear, disconnect dolly air/electric, unlock fifth wheel
• B. Just pull dolly out
• C. Disconnect at high speed
• D. Skip lines

What is the proper way to combine triples?

• A. Couple front trailer to tractor, then dolly + middle, then dolly + rear
• B. Couple rear first
• C. Couple all simultaneously
• D. Couple by length

When parking a doubles combination, you should:

• A. Park in a straight line, set brakes, chock wheels
• B. Park at angle
• C. Skip chocks
• D. Skip brakes

What is the most dangerous condition for doubles/triples?

• A. High wind crossings, slippery roads, sharp turns
• B. Light traffic
• C. Sunshine
• D. Highway driving

Why should you keep speeds modest in doubles?

• A. Sway amplification grows with speed
• B. Fuel use
• C. Driver fatigue only
• D. Tires wear

Doubles and triples often require:

• A. Special permits for certain routes and lengths
• B. No permits
• C. Reduced cargo only
• D. Annual licensing only

What is a "Rocky Mountain Double"?

• A. Tractor with a long lead trailer and short pup behind
• B. Mountain road
• C. Doubles permit
• D. Type of tractor

What is a "Turnpike Double"?

• A. Two long trailers (typically 48 ft) on a tractor
• B. Tollway sticker
• C. Mountain double
• D. Type of tank

When backing doubles, you should:

• A. Avoid if possible — extremely difficult; uncouple if needed
• B. Back fast
• C. Use trailer brake only
• D. Steer hard

What does a converter dolly's pintle hook attach to?

• A. Lead trailer's pintle eye and supports the second trailer's kingpin
• B. Tractor
• C. Frame only
• D. Fifth wheel only

When inspecting safety chains, look for:

• A. Cracks, broken links, proper connection
• B. Color
• C. Brand
• D. Length only

Why is the rear trailer most vulnerable in a triples?

• A. Sway is amplified through each preceding trailer
• B. It is heavier
• C. It has weaker brakes
• D. It is wider

What is a "stinger" in trailer terminology?

• A. Drawbar device used in some doubles
• B. Brake part
• C. Hitch tool
• D. Air valve

What is "tracking" with doubles?

• A. How well trailers follow the tractor through curves
• B. Speed
• C. Tire wear
• D. Trailer GPS

When pulling doubles, you should never:

• A. Make quick lane changes
• B. Use turn signals
• C. Stop at signals
• D. Carry cargo

What is the safest type of road for doubles/triples?

• A. Open highways with mild grades and gentle curves
• B. Mountain roads
• C. City streets
• D. Two-lane country roads

What is the proper posture when driving doubles in heavy traffic?

• A. Increase following distance, plan lane changes well in advance
• B. Tailgate
• C. Speed up
• D. Tail other trucks

Why must dolly air lines and electrical be checked daily?

• A. Critical for brakes and lights on the trailing trailer
• B. Looks
• C. Fuel use
• D. Speedometer

When handling doubles in a crosswind, you should:

• A. Slow down, hold steering firmly, anticipate sway
• B. Speed up
• C. Steer hard against wind
• D. Brake hard

When approaching a long downgrade with doubles, you should:

• A. Reduce speed and select a lower gear earlier than singles
• B. Coast in neutral
• C. Use only trailer brake
• D. Speed up to maintain momentum

What is the safest action if a trailer begins to sway in doubles?

• A. Ease off accelerator without braking
• B. Brake hard
• C. Steer sharply
• D. Speed up

Why do many states restrict triples to specific roads?

• A. Length and handling characteristics increase risk on tight roads
• B. Driver shortage
• C. Fuel use
• D. Tradition

What is the typical maximum length for doubles in most states?

• A. About 28-29 ft per trailer (pups)
• B. 53 ft each
• C. 40 ft each
• D. 20 ft each

What is a "Western Double" or "Standard Double"?

• A. Tractor with two pup trailers (28-29 ft each)
• B. Tank doubles
• C. Reefer doubles
• D. Auto doubles

What is the safest way to cross railroad tracks with doubles?

• A. Slow approach, no shifting on tracks, full clearance before stopping
• B. Speed up
• C. Stop on tracks
• D. Shift on tracks

What is the danger of a dolly with bad tires?

• A. Sway, blowouts, brake imbalance
• B. Cosmetic only
• C. Fuel use only
• D. Engine RPM

What is "kingpin lock"?

• A. Mechanism that secures the trailer kingpin in fifth wheel jaws
• B. Brake lock
• C. Axle lock
• D. Steering lock

You can prevent jackknife in doubles by:

• A. Smooth braking, avoiding skids, slower in turns
• B. Hard braking
• C. Skidding intentionally
• D. Speeding up

What is "trailer-trailer angle"?

• A. Angle between connected trailers in a double or triple
• B. Camber angle
• C. Caster angle
• D. Steering angle

When parking doubles on a slope, you should:

• A. Avoid; if necessary, chock wheels both directions
• B. Park anywhere
• C. No chocks needed
• D. Use parking brake only

What is the proper way to start moving a doubles after a stop?

• A. Smooth, gentle accelerator to avoid sway
• B. Floor it
• C. Pump throttle
• D. Use trailer brake

If you must back a doubles, what should you do first?

• A. Uncouple if at all possible
• B. Just back slowly
• C. Use a helper alone
• D. Open trailer doors

Why is the dolly tongue weight important?

• A. Affects handling and load transfer
• B. For looks
• C. Fuel use
• D. Tire pressure

Why have safety chains when an air-line break occurs?

• A. Air-line break alone won't stop separation; chains keep dolly attached
• B. For brake feel
• C. For decoration
• D. For weight

When uncoupling lead trailer with second trailer attached, you should:

• A. Park combination first, uncouple second trailer first, then lead
• B. Uncouple lead first
• C. Disconnect all at once
• D. Skip parking brake

What is "centerline-tracking"?

• A. Each trailer tracks the path of the tractor in straight line
• B. Highway lanes
• C. GPS path
• D. Center of gravity

Why are doubles brakes balanced?

• A. So each trailer brakes proportionally — proportioning valves
• B. Random distribution
• C. Brake pedal force only
• D. No balancing

When pulling triples, the speed should be:

• A. Lower than singles especially in wind, curves, and slopes
• B. Higher
• C. Same
• D. Highway speed

What does the term "LCV" mean?

• A. Longer Combination Vehicle — typically two long trailers or triples
• B. Light Commercial Vehicle
• C. Liquid Cargo Vehicle
• D. Local Cargo Vehicle

Why are LCVs often restricted to specific states?

• A. Public safety and infrastructure capacity differ by state
• B. Federal preference
• C. Random rule
• D. Toll cost

When uncoupling, which fifth wheel is released last?

• A. Tractor-to-front-trailer fifth wheel
• B. Dolly-to-trailer fifth wheel
• C. Doesn't matter
• D. All at once

What can cause sudden trailer separation in doubles?

• A. Improper coupling, missing lock or chains, broken pintle hook
• B. Wind only
• C. Heavy load only
• D. Clean roads

What angle should the dolly be in when coupling?

• A. Straight aligned with the trailer
• B. Slightly turned
• C. 45 degrees
• D. Any angle

What is "trailer slip" angle?

• A. Angle between trailer wheels and direction of travel during sway
• B. Camber
• C. Caster
• D. Toe

When coupling lead trailer to dolly, you should:

• A. Back tractor and lead trailer to dolly's pintle eye carefully
• B. Push dolly to lead trailer
• C. Drag dolly
• D. Lift by hand

How can you reduce sway-induced rollover risk?

• A. Slow down in turns, smooth steering, balanced loads
• B. Speed up
• C. Brake hard
• D. Sharp steering

Glad hands on doubles must be:

• A. Color matched and locked, no leaks
• B. Either color
• C. No locks needed
• D. Hand tightened

What is a "B-train"?

• A. Combination with a fifth wheel mounted on a deck attached to the lead trailer
• B. A type of train
• C. A brake system
• D. A B class license

Why are B-trains considered more stable than A-trains?

• A. Fewer pivot points reduce sway
• B. Stronger steel
• C. Bigger engine
• D. Wider tires