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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.1.1 Rollover Risks, printed page 6-1 (physical PDF page 1) ↗
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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.1.2 Steer Gently; continued printed 6-2, printed page 6-1 (physical PDF page 1) ↗
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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.1.3 Brake Early, printed page 6-2 (physical PDF page 2) ↗
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
Get everyone out of the vehicle and away from the tracks. From safety, call for emergency help and provide the crossing location, including its posted DOT identification when available.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.1.4 Railroad-Highway Crossings, printed page 6-3 (physical PDF page 3) ↗
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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.1.5 Prevent Trailer Skids — Recognize the Skid, printed page 6-3 (physical PDF page 3) ↗
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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.1.5 Prevent Trailer Skids — Stop Using the Brake, printed page 6-3 (physical PDF page 3) ↗
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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.1.6 Turn Wide, printed page 6-3 (physical PDF page 3) ↗
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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.1.7 Backing with a Trailer, printed page 6-4 (physical PDF page 4) ↗
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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.2.1 Trailer Hand Valve, printed page 6-5 (physical PDF page 5) ↗
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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.2.2 Tractor Protection Valve, printed page 6-5 (physical PDF page 5) ↗
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: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.2.3 Trailer Air Supply Control, printed page 6-5 (physical PDF page 5) ↗
What are the two air lines connecting the tractor and trailer in an air-braked combination?
Correct answer: Service and emergency
The service line carries brake-control pressure, while the emergency line supplies tanks and controls emergency braking.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.2.4 Trailer Air Lines, printed page 6-6 (physical PDF page 6) ↗
What happens when pressure is lost from the trailer emergency line?
Correct answer: Trailer emergency braking and tractor protection activate
Loss of supply-line pressure triggers trailer emergency braking and protects the tractor air supply.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.2.4 Trailer Air Lines — Emergency Air Line, printed page 6-6 (physical PDF page 6) ↗
Which color normally identifies the trailer emergency air line?
Correct answer: Red
Emergency or supply lines are normally red; service lines are normally blue.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.2.4 Trailer Air Lines; 6.2.5 Hose Couplers (Glad Hands), printed page 6-6 (physical PDF page 6) ↗
What danger can result from crossing the trailer service and emergency air lines?
Correct answer: Tanks may not charge; brakes may fail
Crossed connections may prevent spring-brake release or, on older trailers, allow movement without trailer brakes.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.2.5 Hose Couplers (Glad Hands); continued printed 6-7, printed page 6-6 (physical PDF page 6) ↗
During normal operation—not an airflow test—how should trailer air-line shut-off valves be positioned in a multi-trailer combination?
Correct answer: Open through the rig; closed at the final rear
Air must pass through each unit, so intermediate shut-off valves remain open. Close the unused service and supply outlets at the rear of the last trailer. Opening those final valves temporarily to test airflow is a separate inspection step.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.2.7 Shut-off Valves; 6.5.2 Check That Air Flows to All Trailers (printed 6-14), printed page 6-7 (physical PDF page 7) ↗
Why must wheel chocks be used when parking an older trailer without spring brakes?
Correct answer: Stored air can leak away and release its emergency brakes
Air-operated emergency brakes on such trailers hold only while stored pressure remains.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.2.8 Trailer Service, Parking and Emergency Brakes, printed page 6-7 (physical PDF page 7) ↗
Where is a trailer’s yellow ABS malfunction lamp normally located?
Correct answer: Left-side front or rear corner
A trailer ABS malfunction lamp is yellow and located on the left side near a front or rear corner. Do not confuse it with the red trailer-air-supply control in the tractor cab.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.3.1 Trailers Required to Have ABS, printed page 6-8 (physical PDF page 8) ↗
Why must a fifth-wheel plate that requires grease be properly lubricated before coupling?
Correct answer: Excess friction can create steering problems
Where lubrication is required, excess friction between the tractor and trailer can cause steering problems. Learn the coupling details and maintenance requirements for the equipment you operate.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.4.1 Coupling Tractor-Semitrailers — Step 1 Inspect Fifth Wheel, printed page 6-9 (physical PDF page 9) ↗
How should the trailer height be set before backing fully under it?
Correct answer: Low enough to be raised slightly by the tractor
Set the trailer so the tractor raises it slightly while backing under. Too high can prevent proper coupling; too low can damage the trailer nose. Check kingpin and fifth-wheel alignment.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), section 6.4.1 Coupling Tractor-Semitrailers — Step 6 Check Trailer Height, printed page 6-10 (physical PDF page 10) ↗
