During normal operation, how should the rear air-line shut-off valves be set in a doubles combination?
Correct answer: Lead trailer open; final trailer closed
Air must flow through intermediate units, while unused ends at the last trailer stay closed.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), 7.3 Inspecting Doubles and Triples — Double and Triple Trailers, printed page 7-6 (physical PDF page 6) ↗
Which list identifies converter-dolly connections that must be checked?
Correct answer: Pintle connections, chains, air lines, light cords
All dolly connections must be latched, supported, connected, and undamaged.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), 7.3 Inspecting Doubles and Triples — converter-dolly connections (continued), printed page 7-7 (physical PDF page 7) ↗
How is emergency-line airflow verified at the back of a doubles rig?
Correct answer: Charge the system and briefly open the last trailer’s emergency shut-off to hear escaping air
Secure the rig with the tractor parking brake and/or wheel chocks, build normal pressure and push in the trailer-air-supply control. Briefly open and close the last emergency-line valve; escaping air shows supply reaches the rear. Test the service line separately with the hand control or service pedal applied, and close its valve afterward.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), 7.4.1 Additional Air Brake Checks — Check That Air Flows to All Trailers, printed page 7-7 (physical PDF page 7) ↗
At approximately what pressure range does the trailer-air-supply control usually pop out during its test?
Correct answer: 20 to 45 psi
The exact value follows the manufacturer, but the handbook gives a usual 20-to-45-psi range.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), 7.4.1 Additional Air Brake Checks — Test Tractor Protection Valve, printed page 7-7 (physical PDF page 7) ↗
On a combination equipped with a trailer hand control, how should the trailer service brakes be tested?
Correct answer: Move forward slowly and apply the trailer hand control to feel the brakes engage
At normal air pressure with parking brakes released, move forward slowly and apply the hand control, if equipped. Feel the trailer brakes engage. Use the foot pedal for normal braking, not the hand control.
Source: New York State Commercial Driver's Manual CDL-10 (11/25), 7.4.1 Additional Air Brake Checks — Test Trailer Service Brakes, printed page 7-7 (physical PDF page 7) ↗
