CDL Combination Vehicles Test
Driving combinations safely: practice questions
Our CDL Combination bank has 50 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.
Question 1
What is a bobtail tractor?
- A tractor without a semitrailer
- A tractor pulling two trailers
- A tractor with a sleeper berth
- A tractor with a single drive axle
Show the answer
A. A tractor without a semitrailer — Bobtail tractors are tractors without semitrailers (CDL Manual 6.1.3)
Question 2
What is the manual's advice for avoiding panic stops in a combination rig?
- Use the trailer hand valve for early stops so the trailer stays straight
- Keep the trailer lightly loaded
- Brake hard and late to save time
- Allow lots of following distance and look far ahead
Show the answer
D. Allow lots of following distance and look far ahead — Allow lots of following distance and look far ahead so you can brake early (CDL Manual 6.1.3)
Question 3
Compared with empty rigs, how much more likely are fully loaded rigs to roll over in a crash?
- Twice
- Five times
- Twenty times
- Ten times
Show the answer
D. Ten times — Fully loaded rigs are ten times more likely to roll over in a crash than empty rigs (CDL Manual 6.1.1)
Question 4
What rearward amplification does the manual give for triples?
- 3.5
- 2.0
- 1.5
- 5.0
Show the answer
A. 3.5 — Triples have a rearward amplification of 3.5, so you can roll the last trailer 3.5 times as easily as a five-axle tractor (CDL Manual 6.1.2)
Question 5
What is off-tracking?
- The rear wheels following a different path than the front wheels in a turn
- The trailer drifting out of its lane at highway speed
- The trailer bouncing off the road on a bump
- The tractor sliding sideways on ice
Show the answer
A. The rear wheels following a different path than the front wheels in a turn — When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels; this is off-tracking or cheating (CDL Manual 6.1.6)