CDL Practice Test
CDL - Commercial Driver's License CDL Combination Vehicles Practice Test 3
When coupling a tractor to a semi-trailer, what is the correct order for connecting the air lines?
Select your answer
A
Connect the emergency (red) line first, then the service (blue) line
B
Connect the service (blue) line first, then the emergency (red) line
C
Connect both lines simultaneously to avoid pressure loss
D
Order does not matter as long as both lines are connected before moving
Hint