UniDrive Test

What is the only tractor air system failure that will cause a service circuit's brakes not to work during a service application?

None of the above
Secondary service circuit failure
Primary service circuit failure
Emergency brake failure

Foundation brakes are the mechanical component at the axle ends. If they are not working properly, what happens?

The driver should find a place to come to a safe stop
The driver should apply the park brakes
The air brake system will not be able to stop the vehicle
The driver will need to use the emergency brakes to stop the vehicle

What will cause the glad hand couplers to leak?

If the couplers are not attached securely
If the air pressure is too much
If the seals are soft or degraded
If the seals are the wrong size

If there is any doubt about the security of the glad hand couplers during coupling, pre-trip and en-route inspections, what should happen?

Drive with caution until more evidence is gathered
The Inform your employer
Repairs must be made immediately
Add it to the report

During a secondary service circuit failure, which brakes will not apply?

The drive axel brakes
The trailer brakes
The steering axle brakes
All of the brakes

Is the trailer supply valve part of the tractor's protection system?

Yes
Straight trucks only
No
Only if towing tandem trailers

Why do flat deck haulers run the trailer air lines from the back of the frame to the landing leg area of the trailer, rather than from the back of the cab to the nose of the trailer?

It's the straightest path
No reason
It's the shortest path
Causes less interference from loads that overhang the front of the deck

What will enforcement officers during Level 1 Commercial Vehicle Safety Alliance (CVSA) inspection will check?

Both parts of the tractor's protection system
The psi of the primary tank
The psi of the secondary tank
The couplers

What year did were spring park brakes required on trailers?

1986
1996
1976
1981

How are failures in the supply circuit recognized?

During pre-trip inspections
After a post-trip inspection
The air pressure gauges not replenishing when the air pressure gets below the governor cut-in level
During brake failure

What is the minimum lining thickness for brake linings from the Commercial Vehicle Safety Alliance (CVSA) roadside inspection out-of-service criteria?

1/2 inch (13 mm)
3/4 inch (19 mm)
1/4 inch (7 mm)
3/8 inch (9.5 mm)

If the trailer service brakes are not working and the vehicle must be stopped quickly, what should the driver do?

Pump the brakes
Take a longer route to stop the vehicle
Pull the trailer air supply valve
Apply the mechanical brakes

Having a very powerful emergency brake, twice as powerful as spring park brakes, what is the risk?

Brake lockup in an emergency application
Brake failure on the trailers
Having a load shift in an emergency
Brake failure on the tractor

What do glad hand couplers do?

None of the above
Connects the air lines to the cylinders
Connects the air lines to the trailer
Connects the air dryer to the air lines

When would the dash park control valve be used?

Parking on a grade
Overnight parking
Poor road conditions
Any situation where there is a loss of service brakes and a quick stop is required

What does the service/control line do?

None of the above
Blocks the control system
Carries the control system from the foot valve to the trailer service circuit relays
Disconnects the trailer service relays

What will a failure in the park circuit will cause?

Trailer brakes only will lose air pressure
Park and emergency brake service circuits to lose air pressure
All brakes will lose air pressure
Parking brakes only will lose air pressure

What can you do to remove contamination before attaching the glad hand couplers?

Shake the couplers for 10 seconds each before connecting the glad hand couplers to shake the contamination out
A quick discharge of air pressure before connecting the glad hand couplers to blow contamination out
Blow into the couplers
Nothing

If there is any sign that the trailer service brakes are not working and the vehicle must be stopped quickly, what should the driver do?

Apply the park brakes
Pull the trailer supply valve
Downshift
Pump the pedal

During a roadside inspection, what happens if the trailer air supply valve does not work properly?

The vehicle must return to the yard
The employer receives a ticket
The driver receives a ticket
The vehicle will be placed out-of-service

What should glad hand couplers have on them when not pulling a trailer?

None of the above
Semi-automatic couplers
Dead-end couplers
Full-automatic couplers

What is the problem with air pressure park brakes?

Air pressure drains out of the system, the park brakes will release
Not enough pressure to park
None of the above
They are not as tight as spring brakes

Pushing in the trailer air supply valve (red button) with the park control valve (yellow button) pulled during these vehicle inspections will allow what to happen?

The primary tank is low in air pressure
The driver will know if lines were crossed
The secondary tank is low in air pressure
Any air leaks to be noticed and dealt with before the equipment is put into service

What do the air lines that connect to the trailer carry?

Hydraulic fluid
Most of the air supply
All of the air supply only
The air supply and the brake signal to the trailer service and park circuits

During emergency braking, which statement is false?

Monitoring air pressure gauges for proper operation
Pump the brake pedal until air builds up in the lines
When safely stopped, the vehicle should not be driven until repairs are completed
Hold a steady brake application to avoid additional loss of air

What does the tractor protection valve do?

Closes off the service line
Controls the supply line
Uses supply line pressure to open the service line
Stops air pressure from entering the lines

Whats the purpose of the slack adjuster?

It automatically adjusts the slack in the brake lines
It forces the air intake valve
It converts push rod force from the chamber to torque on the s-cam shafts
None of the above

If the trailer does lose traction during a trailer supply line failure, what happens?

None of the above
It will take three times as long to stop in a straight line
The trailer will swing
The ABS will activate

Rather than using mechanical spring park brakes to hold the foundation brakes on for the emergency brake, what can be done instead?

Air from the service tank is supplied to the service chambers
Increase the diameter of the air hoses
Nothing can be done
Increase the size of the brake pads

What can become a problem of a tractor using coiled plastic air lines?

They are often too short and will stretch, causing the lines to shrink in diameter
They become brittle over time
Nothing
They become tough to attach to the trailers

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