Correct answer: C. – It performs both functions
The emergency, or supply, line carries air needed to charge the trailer air tanks. It also controls the trailer’s emergency brakes. A major pressure loss in this line causes the trailer emergency brakes to apply, while loss of supply air can also activate the tractor-protection system.
Source: Commercial Driver License Manual — § 6.2.3, “Trailer Air Lines”
Correct answer: B. – Cargo and its securement should be checked after every driving break
Check the cargo and securement devices within the first 50 miles after beginning the trip. Recheck them as often as necessary, including after three hours or 150 miles and after every driving break. Federal rules contain exceptions when cargo is sealed against inspection or loaded in a way that makes inspection impracticable.
Source: Commercial Driver License Manual — § 3.1.4, “Cargo Checks”, 49 CFR § 392.9(b) — Inspection of Cargo, Cargo Securement Devices and Systems
Correct answer: D. – Do not react and make every reasonable effort to get out of the driver’s way
Make every attempt to get out of an aggressive driver’s way. Do not challenge the driver by speeding up or trying to hold your position, and avoid eye contact. Ignore hostile gestures rather than responding. When it can be done safely, report the vehicle description, license number, location, and direction of travel to law enforcement.
Source: Commercial Driver License Manual — § 2.10.3, “What You Should Do When Confronted by an Aggressive Driver”
Correct answer: A. – 85 to 100 psi
At the engine’s operating rpm, a dual air system should normally build pressure from 85 to 100 psi within 45 seconds. Vehicles with air tanks larger than the minimum size may require more time and still be safe. In that situation, use the vehicle manufacturer’s specifications to evaluate the buildup rate.
Source: Commercial Driver License Manual — § 5.3.3, “Check Rate of Air Pressure Buildup”
Correct answer: B. – False
Do not remove a radiator cap or open another part of a pressurized cooling system until the system has cooled. Steam and boiling coolant can escape under pressure and cause serious burns. A separate coolant-recovery or overflow container that is not part of the pressurized system is different and may be opened as directed by the manufacturer.
Source: Commercial Driver License Manual — Section 2, “Driving in Very Hot Weather”
Correct answer: C. – Continue backing until the vehicle strikes the dock or rear boundary
Back slowly and toward the driver’s side whenever practical because that side provides better visibility. A helper should remain where the driver can see them, and both should agree on hand signals before backing. In Arkansas’s alley-dock exercise, the rear of the vehicle must stop in the designated three-foot area without touching the boundary lines or cones.
Source: Commercial Driver License Manual — § 2.2.2, “Backing Safely”, Commercial Driver’s License Manual Supplement for Modernized Version — “Alley Dock”
