What is the purpose of the tug test right after coupling?

• A.To test how fast the combination can accelerate
• B.To check that the radio works in both units
• C.To warm up the trailer tires
• D.To confirm the fifth wheel jaws have locked onto the kingpin by pulling gently against the trailer brakes

Why

A gentle pull with the trailer brakes set tries to separate tractor and trailer in a controlled way. If the jaws are not locked, it is far better to find out in the yard at walking speed than on the road.

Manual topic: Combination Vehicles - Coupling · From the General Knowledge practice bank (GK-132).

Practice this subject as a full test

More Coupling Basics questions

• Before backing under a semitrailer, what should you check about the trailer height?
• After coupling, why must you get out and visually inspect the fifth wheel jaws and release handle?
• What danger does a gap between the trailer apron (upper coupler plate) and the fifth wheel plate indicate?
• When connecting the air lines, why do you connect the glad hands with the seals facing each other and turn them about a quarter turn?
• Which glad hand supplies the air that fills the trailer tanks and releases the trailer spring brakes?