Try a DVSA HGV / LGV practice theory test question from the Braking Systems DVSA topic

Your tractor unit has three air lines. You're connecting to a trailer that has two air-line couplings. What colour is the line you shouldn't connect to the trailer?

Select one of these four answers before moving on to the next question.

View the DVSA HGV / LGV theory test explanation

This DVSA explanation shows you why the correct answer is right (and the others are wrong), so you can understand the information around the question and remember it for the real HGV / LGV theory test.

Reveal the DVSA HGV / LGV theory test explanation
When connecting a three-line tractor unit to a two-line trailer, the blue line is the one that shouldn't be connected to the trailer. This is the auxiliary line. Always follow the manufacturer's advice: it may be necessary to reconnect the extra line to the tractor unit.

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This is DVSA HGV / LGV revision theory test question 97 of 104 from our free UK HGV / LGV practice theory test. This practice test follows the same format as the real DVSA multiple-choice HGV / LGV theory test.

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