CDL COMBINATION VEHICLES III
CERTIFICATION ASSESSMENT 2026 VERIFIED
ANSWERS GRADED A+
◉ You are driving a combination vehicle when the trailer breaks
away, pulling apart both air lines. You would expect the trailer
brakes to come on and ...
1. the tractor to lose all air pressure
2. the tractor protection valve to close
3. the trailer supply valve to stay open.
Answer: the tractor protection valve to close
◉ When you drive a set of doubles, which shut-off valve must be
closed in the last trailer?
1. Middle section
2. front section
3. back section.
Answer: back section
◉ The fifth wheel locking lever is not locked after the jaws close
around the kingpin. This means that...
1. the parking lock is off and you may drive away
, 2. the trailer will not swivel on the fifth wheel
3. the coupling is not right and should be fixed before you drive the
coupled unit.
Answer: the coupling is not right and should be fixed before you
drive the coupled unit
◉ What gear should the tractor engine be in after you uncouple the
trailer and are inspecting the trailer?
1. neutral
2. low reverse
3. high reverse.
Answer: neutral
◉ After you supply air to the trailer, make sure the air lines are not
crossed and the trailer brakes are working. This is done by ..
1. lifting the brake pedal
2. applying and releasing the trailer brakes and listening for brake
sounds
3. turning on the parking brake from the cab.
Answer: applying and releasing the trailer brakes and listening for
brake sounds
◉ If the brakes did not release when you pushed the trailer air
supply valve, you should ...
CERTIFICATION ASSESSMENT 2026 VERIFIED
ANSWERS GRADED A+
◉ You are driving a combination vehicle when the trailer breaks
away, pulling apart both air lines. You would expect the trailer
brakes to come on and ...
1. the tractor to lose all air pressure
2. the tractor protection valve to close
3. the trailer supply valve to stay open.
Answer: the tractor protection valve to close
◉ When you drive a set of doubles, which shut-off valve must be
closed in the last trailer?
1. Middle section
2. front section
3. back section.
Answer: back section
◉ The fifth wheel locking lever is not locked after the jaws close
around the kingpin. This means that...
1. the parking lock is off and you may drive away
, 2. the trailer will not swivel on the fifth wheel
3. the coupling is not right and should be fixed before you drive the
coupled unit.
Answer: the coupling is not right and should be fixed before you
drive the coupled unit
◉ What gear should the tractor engine be in after you uncouple the
trailer and are inspecting the trailer?
1. neutral
2. low reverse
3. high reverse.
Answer: neutral
◉ After you supply air to the trailer, make sure the air lines are not
crossed and the trailer brakes are working. This is done by ..
1. lifting the brake pedal
2. applying and releasing the trailer brakes and listening for brake
sounds
3. turning on the parking brake from the cab.
Answer: applying and releasing the trailer brakes and listening for
brake sounds
◉ If the brakes did not release when you pushed the trailer air
supply valve, you should ...