Two compatible semitrailers will form a set of doubles. One carries a much heavier load. Which order does the manual recommend for the safest handling?
Correct answer: Put the heavier trailer directly behind the tractor
The more heavily loaded semitrailer belongs in the first position behind the tractor, with the lighter one behind it. Working brakes do not make trailer order irrelevant to handling.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-1, physical 96 > 7.2.1 Coupling Twin Trailers, trailer-loading order paragraph. ↗
On a slippery grade, why does adding trailers call for extra caution even though the combination now has more axles?
Correct answer: The drive axles must pull more unpowered axles
The manual describes greater length and more dead, or unpowered, axles for the drive axles to pull. Additional trailer axles do not become powered axles, and adverse conditions increase the chance of skids and lost traction.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-1, physical 96 > 7.1.6 Adverse Conditions. ↗
Several parking spaces are long enough for your doubles, but some end at a wall. Which feature should guide your choice before entering a space?
Correct answer: A clear route that lets the combination pull straight through
For doubles and triples, the manual emphasizes choosing a place with a straight-through exit. Space to fit the parked rig alone does not establish that it can leave without a difficult backing maneuver.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-1, physical 96 > 7.1.7 Parking the Vehicle. ↗
A converter dolly has spring brakes and is ready to be repositioned under controlled conditions. Which release method does the manual specify for that design?
Correct answer: Use the dolly's parking-brake control
The manual distinguishes a dolly with spring brakes from the other dolly arrangement it describes. For the spring-brake-equipped dolly, use its parking-brake control; do not transfer the tank-drain release instruction to that design.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-2, physical 97 > 7.2.1 Position Converter Dolly in Front of Second (Rear) Trailer, brake-design alternatives. ↗
The first trailer has towed an empty converter dolly close to the second trailer for positioning. No rear trailer rests on the dolly yet. Before unhooking this dolly from the first trailer, what should happen to its support?
Correct answer: Lower the dolly support before unhooking
In this positioning method, the dolly support is raised for towing and lowered before the dolly is unhooked. This scenario concerns an unloaded dolly; it does not authorize releasing a pintle hook while a rear trailer is still on the dolly.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-2, physical 97 > 7.2.1 Position Converter Dolly in Front of Second (Rear) Trailer, tractor/first-semitrailer positioning sequence. ↗
A rear trailer is secured with its brakes locked and wheels chocked. Its height would let the converter dolly pass underneath without lifting the trailer at all. What adjustment is needed before coupling?
Correct answer: Lower it so the dolly will raise it slightly
The trailer should be slightly lower than the center of the dolly's fifth wheel so that backing the dolly underneath raises it slightly. The kingpin is part of the connection; it does not replace contact between the fifth-wheel plates.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-3, physical 98 > 7.2.1 Connect Converter Dolly to Rear Trailer, securement and height checks. ↗
A twin-trailer driver has inspected the tractor's fifth wheel but has not examined the converter dolly's fifth wheel. How complete is the coupling inspection?
Correct answer: Incomplete; the dolly's fifth wheel also needs inspection
The dolly has its own fifth-wheel coupling to the rear trailer. Doubles add critical components, and a satisfactory tractor coupling or successful movement does not establish that the dolly coupling passes its inspection.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-1, 7-2 and 7-4, physical 96, 97 and 99 > 7.1.3 Inspect Completely; Figure 7.1; 7.3.1 Coupling System Areas. ↗
A dolly's pintle-hook latch looks closed, but the dolly's eye is not seated in the hook. What does this mean for the connection?
Correct answer: It is incorrect and must be corrected before travel
The inspection calls for both the dolly eye to be in the trailer's pintle hook and the hook to be latched. A closed-looking latch or weight on the dolly does not make an unseated eye a correct connection.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-4, physical 99 > 7.3.1 Additional Checks, Double and Triple Trailers, pintle-eye and hook-latch checks. ↗
A spare tire sits in the converter dolly's carrier, but its retaining device is loose. What should be done before departure?
Correct answer: Secure the spare tire in its carrier
When a spare tire is carried on the converter gear, the manual requires checking that it is secured. Its weight and the dolly's need to articulate do not justify a loose tire.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-4, physical 99 > 7.3.1 Additional Checks, Double and Triple Trailers, spare tire on converter gear. ↗
A double is straight on firm, level ground and secured for uncoupling. Before the dolly is withdrawn from beneath the rear trailer, how should that trailer's landing gear be positioned?
Correct answer: Lowered enough to take some weight off the dolly
The rear-trailer uncoupling sequence lowers its landing gear enough to remove some weight from the dolly before the dolly is released and pulled out. These support steps accompany the specified brakes, chocks, line disconnections and latch sequence.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-3, physical 98 > 7.2.2 Uncoupling Twin Trailers, Uncouple Rear Trailer. ↗
The rear trailer's landing gear has been lowered, but the converter dolly remains under it. A helper proposes opening the first trailer's pintle hook now. What should the driver do?
Correct answer: Keep the pintle locked until the dolly is out
Never unlock the pintle hook with the dolly still beneath the rear trailer. The tow bar can fly upward and cause injury; lowering landing gear is not permission to reverse the specified uncoupling order.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-3, physical 98 > 7.2.2 Uncouple Converter Dolly, pintle-hook warning. ↗
An unloaded dolly has been pulled clear of the rear trailer and its support is lowered. The dolly has no spring brakes. What restraint is needed before releasing it from the first trailer's pintle hook?
Correct answer: Chock the dolly's wheels
The dolly-uncoupling sequence calls for applying the converter gear's spring brakes or chocking its wheels. With no spring brakes in this scenario, chocks provide the specified wheel restraint; the first trailer's brakes cannot hold a disconnected dolly.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-3, physical 98 > 7.2.2 Uncouple Converter Dolly, support and wheel-restraint sequence. ↗
In a training yard, a three-trailer combination is secured for disassembly using the manual's method. Which part is separated first?
Correct answer: The third trailer, then its dolly, using the doubles procedure
The described method starts by removing the third trailer: pull its dolly out, then unhitch that dolly. The remaining combination is then uncoupled as a double.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-3, physical 98 > 7.2.3 Coupling and Uncoupling Triple Trailers, Uncouple Triple-trailer Rig. ↗
Your assigned combination uses a coupling arrangement different from the common configurations shown in the manual. What should establish its coupling and uncoupling procedure?
Correct answer: The manufacturer or owner's specifications for that vehicle
Section 7 does not cover every truck-trailer arrangement. The driver must learn the correct procedure for the actual equipment according to its manufacturer and/or owner specifications.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-3, physical 98 > 7.2.4 Coupling and Uncoupling Other Combinations. ↗
A secured double has normal tractor air pressure and its trailer supply control is pushed in. During the rear supply-line test, no air escapes at the last trailer. Which possible cause does the manual direct you to check?
Correct answer: Whether an upstream trailer or dolly shut-off is closed
The air path must remain open through the preceding trailer and any equipped dolly shut-offs. Normal pressure at the tractor does not prove that air reaches the last trailer. A closed intermediate valve is a possible cause to check, not the only possible fault.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-4, physical 99 > 7.4.1 Additional Air Brake Checks, Check That Air Flows to All Trailers. ↗
During a secured rear-of-rig air-flow check, the supply line passes. No air comes from the service-line outlet, but neither the handbrake nor foot brake is applied. What must be corrected before judging the service-line result?
Correct answer: Apply the trailer handbrake or service-brake pedal
The service-line flow check assumes the trailer handbrake or service-brake pedal is applied to supply a service signal. With neither applied, silence alone does not establish a blocked line. Keep the rig securely held throughout the check.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-4, physical 99 > 7.4.1 Check That Air Flows to All Trailers, service-line brake-application condition. ↗
The converter dolly's air-tank petcock was opened during positioning on a design that uses that method. Coupling is now being completed. What setting does the manual require for that drain before charging the system for travel?
Correct answer: Closed to retain air in the tank
The coupling sequence closes the dolly's air-tank petcock, and the doubles/triples inspection also requires that drain to be closed. Leaving it open for travel is not a method of regulating brake pressure.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-2, 7-3 and 7-4, physical 97, 98 and 99 > 7.2.1 dolly positioning and Connect Converter Dolly to Rear Trailer; 7.3.1 Double and Triple Trailers, drain-valve check. ↗
Both air-flow checks at the rear of the last trailer have passed. Before leaving that location, how should the service and supply shut-off valves at the very end of the rig be left?
Correct answer: Both closed
Each rear outlet is opened briefly for its test and then closed. The last trailer's end valves must be closed; valves needed to pass air onward through preceding trailers stay open.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-4, physical 99 > 7.3.1 Double and Triple Trailers, shut-off settings; 7.4.1 rear supply and service outlet test sequence. ↗
A driver uses the equipped trailer hand valve for the prescribed slow service-brake check. Once driving normally, which control should provide routine service braking?
Correct answer: The foot-brake pedal
The manual distinguishes the trailer hand-valve check from normal operation. Routine braking uses the foot pedal, which applies service braking at all wheels, rather than using the trailer hand valve alone or the supply control.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-5, physical 100 > 7.4.1 Test Trailer Service Brakes, test-control versus normal-operation paragraph. ↗
In a clear test area, the trailer system was charged and free rolling was confirmed. After stopping and setting the trailer supply control to emergency, the trailers still roll freely under a gentle pull. What does that result show?
Correct answer: The check has not confirmed trailer emergency braking
After the charged system is placed in emergency, the gentle pull checks that the trailer emergency brakes are applied. Continued free rolling fails to confirm that function and requires investigation; the prompt does not identify a particular mechanical fault.
Source: New Jersey CDL Manual, March 2025 cover; Section 7, July 2017 footer, printed 7-5, physical 100 > 7.4.1 Test Trailer Emergency Brakes. ↗
