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Incorrect!

You're driving a tractor unit fitted with two air lines. You want to couple to a trailer that has three air-line couplings. How should the air lines be connected?

The trailer auxiliary line should be left unconnected
Correct answer
The trailer service line should be left unconnected
Only the service line should be connected
Only the auxiliary line should be connected
You selected this answer

DVSA theory test explanation

A two-line system consists of the emergency line (red) and the service line (yellow). You need to understand the rules that apply to safe connection of brake systems and mixing two-line and three-line systems.

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