Which combination best reduces rollover risk in a combination vehicle?
Correct answer: Keep cargo low and slow down for turns
A low, centered load and reduced turn speed keep the center of gravity controlled.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.1.1 Rollover Risks, printed page 6-1 (physical PDF page 89) ↗
What can the crack-the-whip effect do during a sudden lane change?
Correct answer: Cause the rear trailer to overturn
Rearward amplification makes steering movement more severe toward the back of a multi-unit combination.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.1.2 Steer Gently, printed page 6-1 (physical PDF page 89) ↗
Why can an empty combination vehicle be harder to stop smoothly than a fully loaded one?
Correct answer: Light loading can cause wheel lock and poor traction
Light loads can provide poor traction, making wheel lock, trailer swing, and jackknife more likely.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.1.3 Brake Early, printed page 6-1 (physical PDF page 89) ↗
What should a driver do first if a low-clearance combination becomes stuck on railroad tracks?
Correct answer: Leave the vehicle and move away from the tracks
Occupants should get away from the tracks, then use the crossing information to contact emergency services.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.1.4 Railroad-highway Crossings, printed page 6-2 (physical PDF page 90) ↗
What is the earliest reliable sign that a trailer has started to skid?
Correct answer: Trailer misalignment appears in the mirrors
Frequent mirror checks during hard braking reveal trailer swing before a jackknife develops.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.1.5 Prevent Trailer Skids, Recognize the Skid, printed page 6-2 (physical PDF page 90) ↗
How should a driver respond when trailer wheels lock and the trailer starts to swing?
Correct answer: Release the brakes to restore traction
The locked trailer brakes caused the skid; releasing them lets the tires regain grip.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.1.5 Stop Using the Brake, printed page 6-3 (physical PDF page 91) ↗
What does off-tracking mean in a turn?
Correct answer: Rear wheels cut inside the front-wheel path
Long vehicles’ rear wheels cut inside the path of their front wheels, with the last trailer cutting in most.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.1.6 Turn Wide, printed page 6-3 (physical PDF page 91) ↗
When backing a trailer on a curved path, which side is preferred?
Correct answer: The driver’s side
Driver-side backing provides the clearest view; straight-line backing is preferable whenever possible.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.1.7 Backing with a Trailer, printed page 6-3 (physical PDF page 91) ↗
What is the proper routine use of a trailer hand valve?
Correct answer: Testing the trailer brakes
The hand valve is for testing trailer brakes; normal braking should use the foot pedal.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.2.1 Trailer Hand Valve, printed page 6-4 (physical PDF page 92) ↗
What is the tractor protection valve designed to do?
Correct answer: Preserve tractor air after a major trailer leak
The valve closes to protect the tractor air supply when trailer-side pressure is lost.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.2.2 Tractor Protection Valve, printed page 6-5 (physical PDF page 93) ↗
On a newer tractor, what does pulling out the red eight-sided trailer-air-supply knob do?
Correct answer: Shuts off trailer air and applies trailer emergency brakes
Pulling the red knob closes the supply; pushing it in supplies air to the trailer.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.2.3 Trailer Air Supply Control, printed page 6-5 (physical PDF page 93) ↗
What are the two air lines on a combination vehicle?
Correct answer: Service and emergency
The service line carries brake-control pressure, while the emergency line supplies tanks and controls emergency braking.
Source: Florida Commercial Driver's License Manual, July 2022, section 6.2.4 Trailer Air-lines, printed page 6-5 (physical PDF page 93) ↗
