CDL combination vehicles practice test 4

C: Coupling devices used to connect the service and emergency air lines from the tractor to the trailer. Glad hands are the couplers that join the tractor's (or truck's) service and emergency air lines to the trailer. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.5 Hose Couplers (Glad Hands), page 6-5.

A: A rubber seal; clean the couplers and seals first. The couplers have a rubber seal that keeps air from escaping. Clean the couplers and rubber seals before you make a connection. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.5 Hose Couplers (Glad Hands), page 6-5.

C: At a 90-degree angle to each other. Hold the couplers at right angles (90 degrees) to each other, press the seals together, then rotate the hose-side glad hand to join and lock them. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.5 Hose Couplers (Glad Hands), page 6-5.

B: Metal tags stamped 'service' and 'emergency'. Sometimes metal tags with the words 'service' and 'emergency' stamped on them are attached to the lines. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.5 Hose Couplers (Glad Hands), page 6-5.

A: Supply air goes to the service line instead of charging the trailer tanks, so the trailer spring brakes won't release. With crossed lines, supply air is sent to the service line instead of charging the trailer air tanks, so there is no air to release the trailer spring brakes. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.5 Hose Couplers (Glad Hands), page 6-6.

C: The air line connections. If the spring brakes don't release when you push in the trailer air supply control, check the air line connections; they may be crossed. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.5 Hose Couplers (Glad Hands), page 6-6.

A: With the hand valve or by pulling the air supply control, then pulling gently against them in a low gear. Before you drive, set the trailer brakes with either the hand valve or the air supply (tractor protection valve) control, then tug gently against them in a low gear to make sure they hold. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.5 Hose Couplers (Glad Hands), page 6-6.

A: Holding the air hoses when they aren't in use, keeping water and dirt out of the couplers and lines. Dummy couplers hold the hoses when they aren't connected to a trailer, preventing water and dirt from getting into the coupler and air lines. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.5 Hose Couplers (Glad Hands), page 6-6.

C: By the emergency (supply) line from the tractor. Each trailer and converter dolly has one or more air tanks, filled by the emergency (supply) line from the tractor. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.6 Trailer Air Tanks, page 6-6.

A: The pressure in the service line. Air goes from the trailer tanks to the brakes through relay valves, and the service line pressure tells the relay valves how much to send. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.6 Trailer Air Tanks, page 6-6.

C: Open the drains to make sure they are keeping moisture out. Automatic drains remove most of the moisture, but you should still open them to make sure. Tanks with drain valves should be drained every day. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.6 Trailer Air Tanks, page 6-6.

A: Closing off the service and supply air lines at the back of trailers when another trailer isn't being towed. Shut-off valves in the service and supply lines at the back of trailers that tow other trailers let you close off the lines when no other trailer is being towed. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.7 Shut-off Valves, page 6-6.

A: Only the ones at the back of the last trailer. Keep every shut-off valve open except the pair at the very back of the last trailer, which must be closed. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.7 Shut-off Valves, page 6-6.

C: Converter dollies and trailers built before 1975. Newer trailers come with spring brakes, but trailers built before 1975 and converter dollies don't have to have them. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.8 Trailer Service, Parking and Emergency Brakes, page 6-6.

D: Whenever air pressure in the emergency line is lost, the air supply knob is pulled out, or the trailer is disconnected. A trailer without spring brakes uses its stored tank air for emergency braking. Those brakes apply any time the emergency line loses pressure, such as when the air supply knob is pulled or the trailer is disconnected. Commercial Driver's License Manual (CDL Driver's Manual): 6.2.8 Trailer Service, Parking and Emergency Brakes, page 6-6.

B: March 1, 1998. ABS is required on every trailer and converter dolly built on or after March 1, 1998 (also 49 CFR 393.55(c)(2)). Many earlier units were fitted with it voluntarily. Commercial Driver's License Manual (CDL Driver's Manual): 6.3.1 Trailers Required to Have ABS, page 6-6.

C: On the left side of the trailer, on the front or rear corner. Trailers have yellow ABS malfunction lamps on the left side, on either the front or rear corner. Dollies built on or after March 1, 1998 have a lamp on the left side. Commercial Driver's License Manual (CDL Driver's Manual): 6.3.1 Trailers Required to Have ABS, page 6-7.

C: Only when the wheels are about to lock up. ABS is an addition to your normal brakes and only activates when wheels are about to lock up. Commercial Driver's License Manual (CDL Driver's Manual): 6.3.2 Braking with ABS, page 6-7.

D: ABS won't allow you to drive faster, follow more closely, or drive less carefully. ABS is not a license to drive faster, follow closer, or be less careful. Commercial Driver's License Manual (CDL Driver's Manual): 6.3.2 Braking with ABS, page 6-7.

B: It still gives you more control during braking. Even partial ABS, on just the trailer or on a single axle, gives you more control when braking. Commercial Driver's License Manual (CDL Driver's Manual): 6.3.2 Braking with ABS, page 6-7.

A: Rigs differ, and wrong coupling and uncoupling can be very dangerous. There are differences between rigs, and wrong coupling and uncoupling can be very dangerous, so learn the details for the trucks you will operate. Commercial Driver's License Manual (CDL Driver's Manual): 6.4 Coupling and Uncoupling, page 6-7.

B: Without lubrication, friction between the tractor and trailer could cause steering problems. The fifth wheel plate needs grease. Without it, friction between tractor and trailer can make steering difficult. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.1 Coupling Tractor-Semitrailers, page 6-7.

B: Tilted down toward the rear of the tractor, jaws open, and safety unlocking handle in the automatic lock position. For coupling, the fifth wheel should be tilted down toward the rear of the tractor, with the jaws open and the safety unlocking handle in the automatic lock position. A sliding fifth wheel must be locked. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.1 Coupling Tractor-Semitrailers, page 6-7.

A: That it is not bent or broken. Make sure the trailer kingpin is not bent or broken. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.1 Coupling Tractor-Semitrailers, page 6-7.

B: Its wheels are chocked or its spring brakes are on, and any cargo is secured against movement. Make sure the area is clear, the trailer wheels are chocked or the spring brakes are on, and any cargo is secured against movement from the coupling. Commercial Driver's License Manual (CDL Driver's Manual): 6.4.1 Coupling Tractor-Semitrailers, page 6-8.