Use this set after Combination Vehicles Test 1 when trailer movement or coupling decisions still need review.
This second set gives more practice on how a connected trailer changes safe driving, inspection, and control decisions.
Check whether the question is about mechanical connection or vehicle movement.
Visualize where the trailer wheels go during each turn or lane change.
Treat abrupt steering or braking as a rollover and control risk.
When this pattern appears in a missed answer, review the explanation before trying another set.
When this pattern appears in a missed answer, review the explanation before trying another set.
When this pattern appears in a missed answer, review the explanation before trying another set.
When this pattern appears in a missed answer, review the explanation before trying another set.
When this pattern appears in a missed answer, review the explanation before trying another set.
Using the trailer hand valve during normal driving can easily cause the trailer wheels to lock up, which will lead to a trailer jackknife.
Study focusControl off-tracking, rollover, rearward amplification, and trailer movement risks.
Common trapTurning or steering too sharply without accounting for trailer movement.
The red trailer air supply valve is pushed in to supply air to the trailer (releasing the trailer emergency brakes) and pulled out to shut off the air and apply the trailer emergency brakes.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
If only the service (blue) line breaks, you won't notice until you press the brake pedal. Then, air will escape, causing the system pressure to drop until the tractor protection valve closes and the trailer emergency brakes apply.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
If the emergency (red) line breaks, the sudden loss of air pressure in the trailer emergency line will cause the trailer's relay valves to immediately apply the trailer's spring (emergency) brakes.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
Relay valves are used on trailers to speed up the flow of air from the trailer tanks to the trailer brake chambers, minimizing brake lag.
Study focusIdentify key air brake parts and explain how the system produces braking force.
Common trapMemorizing part names without understanding what each part does.
Glad hands are the coupling devices used to connect the service and emergency air lines from the truck or tractor to the trailer.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
Glad hands are connected by pressing the rubber seals together at a 90-degree angle and twisting them until they lock into a straight line.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
Damaged or dirty seals will cause air leaks, which can lead to a loss of air pressure and unexpected application of the emergency brakes.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
When operating bobtail, the glad hands should be attached to dummy couplers to protect the air lines from dirt, water, and insects.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
When you apply and release the trailer hand valve, you should hear the brakes move and hear the air exhaust out of the relay valve at the rear of the trailer.
Study focusIdentify key air brake parts and explain how the system produces braking force.
Common trapMemorizing part names without understanding what each part does.
The trailer must be secured so it doesn't roll backwards when the tractor backs into it. Ensure the spring brakes are on or the wheels are chocked.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
The trailer apron is the solid steel plate located at the front underside of the trailer, which houses the kingpin and rests flat on the tractor's fifth wheel.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
The emergency air line supplies air to release the trailer's spring brakes. Without it connected, the spring brakes stay fully engaged and the trailer wheels are locked. Attempting to drive will damage tires, brakes, and potentially the drivetrain.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
You must check visually that there is enough clearance between the tractor frame and the landing gear, especially for trailers with landing gear mounted close to the front.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
For a loaded trailer, turn the crank a few extra times in low gear after the pads touch the ground. This lifts some weight off the fifth wheel, making it easier to release the latch and pull away.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
For an empty trailer, stop cranking right when the pads make firm contact with the ground. Lifting an empty trailer too high can make it difficult to couple next time.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
To test the tractor protection valve, you fan the brakes to bleed off air pressure. The red knob should pop out, closing the valve to protect the tractor's air supply.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
The locking lever must be fully seated and the safety catch engaged. If it is not, the jaws are not locked securely, and you must not drive the vehicle.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
The kingpin is the thick steel pin located under the front of the trailer (on the apron) that securely engages with the locking jaws of the tractor's fifth wheel.
Study focusRecognize safe coupling, uncoupling, fifth wheel, kingpin, and trailer air-line checks.
Common trapSkipping visual checks after coupling or confusing kingpin contact points.
Connecting the air lines allows you to supply air to the system and then use the trailer brakes (or let the spring brakes hold it) to ensure the trailer stays perfectly still when the fifth wheel pushes against the kingpin.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.