CDL Endorsements Combination Vehicles Practice Questions
Combination Vehicles makes up 10 of every 50 questions on a Tigertest CDL Endorsements practice test. Here are 10 of the 40 questions on it, each with the answer and the reason.
Updated by the Tigertest team. Based on FMCSA CDL Manual sections 4, 5, 6, 8 and 9. HazMat also needs a TSA security threat assessment.
1. According to the CDL manual, what share of truck driver deaths in crashes result from truck rollovers?
- A.Fewer than 5 percent
- B.More than 50 percent
- C.About 10 percent
- D.About 25 percent
Answer: B. The manual states that more than half of truck driver deaths in crashes are the result of rollovers, which is why combination drivers must manage speed and load height.
2. Which two habits does the CDL manual stress to help prevent a combination vehicle rollover?
- A.Take curves at the posted speed limit or faster
- B.Keep trailers empty whenever turning onto ramps
- C.Stack cargo high and toward the curb side for balance
- D.Keep cargo low and centered, and go slow in turns
Answer: D. Rollovers happen when a high, off-center load is turned too fast, so keep cargo as close to the ground as possible and centered, and go slowly around turns.
3. You are pulling triples and must make a quick lane change. Because of the crack-the-whip effect, which trailer is most likely to roll?
- A.The rearmost trailer
- B.The tractor, not any trailer
- C.The first trailer behind the tractor
- D.The middle trailer
Answer: A. Rearward amplification, the crack-the-whip effect, magnifies a quick steering movement toward the back of the rig, so the last trailer is the most likely to turn over.
4. You are driving a set of doubles in heavy traffic and need to change lanes. How should you steer?
- A.Sharply, then countersteer to settle the trailers
- B.With help from the trailer hand valve
- C.Gently, avoiding any sudden steering movements
- D.Quickly, so you spend less time between lanes
Answer: C. Sudden steering can trigger the crack-the-whip effect and roll a trailer, so steer gently; the hand valve should never be used while driving.
5. You are making a tight right turn in a tractor-semitrailer, and the trailer wheels will off-track toward the curb. What should you do?
- A.Cut the corner early so the trailer hugs it
- B.Stop partway and back the trailer around the corner
- C.Turn wide as you complete the turn
- D.Swing wide left before you begin the turn
Answer: C. Trailer rear wheels follow a shorter path than the front wheels, so you turn wide near the end of the turn; swinging left first invites drivers to pass on your right.
6. You drive a 60-foot combination vehicle at 55 mph. Using the manual's rule, what minimum following distance should you keep?
- A.7 seconds
- B.6 seconds
- C.10 seconds
- D.4 seconds
Answer: A. Allow 1 second per 10 feet of vehicle length (6 seconds for 60 feet), then add 1 second because you are above 40 mph, for a total of 7 seconds.
7. Below 40 mph, how much following distance does the manual recommend for each 10 feet of vehicle length?
- A.3 seconds
- B.Half a second
- C.2 seconds
- D.1 second
Answer: D. The rule is at least 1 second for each 10 feet of vehicle length below 40 mph, plus 1 more second above 40 mph.
8. You drive a 50-foot tractor-trailer at 35 mph on a city arterial. What following distance does the manual's rule call for?
- A.8 seconds
- B.5 seconds
- C.3 seconds
- D.6 seconds
Answer: B. At 35 mph you are below 40 mph, so the rule gives 1 second per 10 feet of length, or 5 seconds for 50 feet; the extra second applies only above 40 mph.
9. You drop your trailer and drive the tractor bobtail. How does its stopping distance compare with a fully loaded combination?
- A.It stops shorter because its brakes run cooler
- B.It can take longer to stop
- C.It always stops in half the distance
- D.It stops in exactly the same distance
Answer: B. The manual warns that a bobtail tractor can take longer to stop than a combination loaded to maximum gross weight, because it has little weight on the drive axle for traction.
10. You are pulling an empty flatbed trailer and must slow for traffic. Why does the manual urge extra braking care?
- A.ABS shuts off when a trailer is empty
- B.Empty trailers cannot use their emergency brakes
- C.Empty trailers have no working service brakes
- D.Empty units have less traction and can skid
Answer: D. Brakes, tires and suspension work best when fully loaded; an empty or lightly loaded trailer has less traction, so its wheels lock more easily and can cause a skid or jackknife.
Practice all 40 combination vehicles questions, and the rest of the 200-question bank, in the free CDL Endorsements training sets. Questions you miss come back until you have mastered them.
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