CDL Combination Vehicles Practice Test Part 2

1. Which color coding standard applies to trailer air line connections on a commercial motor vehicle?

2. After backing under a trailer and connecting the fifth wheel to the kingpin, which method confirms that the fifth wheel is properly locked?

3. A driver is preparing to descend a long mountain grade with a loaded tractor-semitrailer. What is the correct use of the trailer hand valve (trolley valve) during this descent?

4. A driver is coupling a tractor to a semitrailer at a loading dock. The driver has positioned the tractor, connected the air lines, supplied air to the trailer, tested the trailer brakes, and backed under the trailer until the fifth wheel engaged. What should the driver do NEXT to complete the coupling procedure safely?

5. A driver is approaching a cloverleaf exit ramp from an interstate highway while operating a loaded tractor-semitrailer with a high center of gravity cargo. The ramp has a posted advisory speed of 25 MPH. What is the safest approach to negotiating this curve to prevent rollover?

6. A driver is traveling on a wet, slippery highway when the tractor begins to skid and the trailer swings outward, creating a jackknife situation where the trailer is pushing the tractor sideways. What is the correct immediate response to recover from this jackknife?

7. A driver has just coupled a tractor to a semitrailer and supplied air to the trailer system. The trailer air tanks have built to full pressure, and the driver wants to test the trailer brakes before proceeding. What is the correct method for testing trailer brake function?

8. A driver couples a tractor to a semitrailer and performs the tug test. When pulling forward gently against the trailer brakes, the trailer moves forward several inches and the driver hears a clunk from the fifth wheel area. The driver stops, inspects the fifth wheel, and finds that the locking lever is not fully in the locked position. What is the most likely cause of this coupling failure, and what should the driver do?

9. A driver is descending a 5% mountain grade in rainy conditions with a loaded tractor-semitrailer. The driver applies the brakes firmly to slow from 45 MPH to 35 MPH, and the tractor immediately begins to skid with the trailer swinging to the right. The driver releases the brakes and counter-steers, but the trailer continues swinging until the combination reaches a full jackknife position. Which factor most likely initiated this jackknife sequence?

10. A tractor-semitrailer rolls over while negotiating an interstate highway curve at 50 MPH. Investigation reveals the following: the cargo was palletized goods loaded to the full height of the trailer (high center of gravity), the curve had an advisory speed of 35 MPH, the driver entered the curve at 50 MPH and did not brake until mid-curve, and the road surface was dry. Which combination of factors contributed most directly to this rollover?

11. A driver needs to uncouple a tractor from a semitrailer at a truck stop. Which step should be performed FIRST in the proper uncoupling sequence?

12. What is the purpose of the tractor protection valve in a combination vehicle’s air brake system?

13. A driver has coupled a tractor to a semitrailer and successfully performed the tug test. The fifth wheel is confirmed locked. What is the correct procedure for raising the landing gear before driving?

14. A driver notices that when applying the service brake pedal, the trailer seems to push against the tractor momentarily before the trailer brakes engage, causing a brief “surge” feeling. What does this symptom indicate about the brake system?

15. A driver operating a twin-trailer combination (doubles) is approaching a right turn onto a narrow two-lane road from a highway. The first trailer is 28 feet long and the second trailer is also 28 feet. Compared to a single 53-foot semitrailer, how does the off-tracking behavior differ for this doubles combination during the turn?

16. A new CDL driver is learning to couple a tractor to a semitrailer. The driver performs the following steps in this order: (1) backs under the trailer until the fifth wheel engages, (2) connects the air lines, (3) raises the landing gear, (4) performs the tug test, (5) connects the electrical cord. What is wrong with this sequence, and what risk does it create?