COMBINATION TEST DISTRICT OF COLUMBIA - PRACTICE TEST
11.
The posted speed limit:
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should never be exceeded.
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may only be exceeded when driving in rural areas.
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should only be exceeded when passing other vehicles.
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is only a suggestion.
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12.
The tractor protection valve:
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controls the emergency brakes on combination vehicles.
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keeps air in the tractor brake system should the trailer break away or develop a bad leak.
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works the trailer brakes.
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supplies air to the trailer air tanks.
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13.
Overloading a vehicle with cargo can have negative effects on all of the following except:
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Speed control
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Braking
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Weight limits
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Steering
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14.
Most heavy vehicles require ________ change gears.
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double shifting
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single clutching
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triple shifting
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double clutching
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15.
The wheels of a large combination vehicle are more likely to lock up when:
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the vehicle is lightly loaded.
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you are traveling in very hot weather.
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the trailer has new tires.
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the vehicle is heavily loaded.
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16.
Which of the following is NOT part of a trailer air line system?
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Emergency air-line
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Kingpin
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Service air-line
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Glad hands
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17.
Under-loaded front axles can:
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cause poor traction.
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cause the drive wheels to spin easily.
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make the steering axle weight too light to steer safely.
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All of the above.
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18.
Emergency brakes must be must be held on by:
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air pressure.
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mechanical force.
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the locking mechanism.
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water.
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19.
Off-tracking is:
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when a vehicle makes a turn and the rear wheels of the trailer end up driving in a different path than the tractor and the front wheels of the trailer.
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when a vehicle towing a trailer skids, and the trailer pushes the towing vehicle from behind until it spins the vehicle around.
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when the tires lose their contact with the road and have little or no traction.
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None of the above.
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20.
When parking a trailer without spring brakes, it is very important for safety that you use wheel chocks. Why?
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if you don't use wheel chocks, supply air will be sent to the service line instead of going to charge the trailer air tanks.
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You may not notice a major leak in the service line until you try to put the brakes on.
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The air could leak out of the trailer air tank, releasing its emergency brakes.
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None of the above.
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